ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Articles  (11,114)
  • Blackwell Publishing Ltd  (5,727)
  • American Institute of Physics (AIP)  (4,045)
  • Institute of Physics
  • Periodicals Archive Online (PAO)
  • Society of Petroleum Engineers
  • 1995-1999
  • 1990-1994  (5,871)
  • 1985-1989  (5,243)
  • 1940-1944
  • 1991  (5,871)
  • 1989  (5,243)
  • Chemistry and Pharmacology  (4,478)
  • Biology  (4,429)
  • Geosciences  (1,991)
  • Technology  (389)
Collection
  • Articles  (11,114)
Source
Publisher
Years
  • 1995-1999
  • 1990-1994  (5,871)
  • 1985-1989  (5,243)
  • 1940-1944
Year
Journal
Topic
  • 1
    Electronic Resource
    Electronic Resource
    The Doppler spectra of O(1D) from the photodissociation of O2, NO2, and N2O (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6218-6223 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Doppler profiles of the O(1D) products from the photodissociation of O2 at 157.6 nm and NO2 and N2O at 205.47 nm are detected by a resonance enhanced multiphoton ionization technique. The translation energy and angular distributions are deduced for the O(1D) atoms. Present results indicate that (a) O2 (B 3Σ−u) has a short dissociative lifetime when irradiated at 157.6 nm, (b) NO(2Π) photofragment from NO2 at 205.47 nm is mostly vibrationally excited, and (c) most of the available energy is released as kinetic energy when N2O is photodissociated at 205.47 nm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461567
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Resonance Raman spectra of the S3←S0 transition of SO2: Electronic, vibrational, and rotational dynamics in solution (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6207-6217 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Resonance Raman spectra, including absolute scattering cross sections, of sulfur dioxide in the vapor phase and in hexane solution have been obtained at several excitation wavelengths between 235 and 208 nm, on resonance with the strong S3←S0, 1B2←1A1 electronic transition. Due to the narrow rovibronic linewidths in the isolated molecule, the vapor phase spectra are best described as single vibronic level resonance fluorescence and exhibit intensity patterns that depend strongly on excitation wavelength, while the solution phase spectra are only weakly dependent on excitation frequency due to the increased linewidths of the vibronic transitions. The spectra in hexane are dominated by long overtone progressions in the symmetric stretch and its combination bands with the bend. The relative and absolute cross sections are reproduced fairly well through time-dependent wave packet propagation calculations employing an anharmonic S3 state potential previously developed to fit vibronic energy levels of the isolated molecule. The average vibronic homogeneous linewidth in solution is found to be about 560 cm−1 FWHM, implying an electronic dephasing time of approximately 20 fs, and the absence of significant broad fluorescence indicates that the dephasing is dominated by electronic population relaxation. In contrast, the ground state isotropic Raman linewidths are less than 5 cm−1, even for overtones involving up to six stretching quanta, indicating ground state vibrational dephasing times greater than 2 ps. Analysis of the anisotropic band shapes suggests that the rotational motion is not greatly hindered by solvation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461566
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    High resolution laser spectroscopy of the B 1Π–X 1Σ+ transition of 23Na85Rb (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6229-6237 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: High resolution spectrum of the B 1Π–X 1Σ+ transition of the NaRb molecule was measured with the technique of the Doppler-free laser polarization spectroscopy. Molecular constants of the B 1Π(v=0–12) and X 1Σ+(v=0–6) states of 23Na85Rb were determined. The energy levels of the B 1Π state were found to present many irregularities due to perturbations. The resonance fluorescence spectrum following an excitation to a strongly perturbed level was measured. The fluorescence to the (1)3Σ+ state, which consists of discrete lines followed by a continuum band, was observed in addition to the fluorescence lines to rovibrational levels of the X 1Σ+ state. The perturbing state to the B 1Π(v=8,J=15–21) levels is identified as the (1)3Π state by comparing the observed fluorescence spectra with the selection rules for perturbations and radiative transitions. The dissociation limit of the (1)3Σ+ state, which separates into the Na(3s2S1/2)+Rb(5s2S1/2) atoms, was deduced from the spectrum. The dissociation energies of the X 1Σ+, (1)3Σ+, and B 1Π states were determined to be 5030±2, 182±2, and 1319±2 cm−1, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461569
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Photoelectron spectroscopy from the A˜ 1Au state of acetylene: The bending vibrations of C2H+2 X 2Πu (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6238-6248 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Photoelectron spectra are reported for one-photon resonant, two-photon ionization of acetylene via a number of vibronic levels of the A˜ 1Au state. Because the A˜ 1Au state is trans bent and the X 2Πu ground state of the ion is linear, ionization from the A˜ 1Au levels produces a long progression in the trans-bending vibration of the ion. The X 2Πu state is split by the Renner–Teller interaction along the trans-bending coordinate; the analysis of the photoelectron spectra allows the determination of the Renner–Teller parameters and leads to reassignments of the cis and trans-bending vibrations in earlier photoelectron studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461570
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Electronic spectroscopy of silver dimer rare gas complexes (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6249-6256 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrationally resolved electronic spectra are reported for the metal dimer-rare gas complexes Ag2–Ar and Ag2–Kr. These spectra are obtained using resonant two-photon photoionization in the energy region near the Ag2 B←X electronic transition (280–285 nm). Both complexes exhibit extensive activity in three vibrational modes, making it possible to determine vibrational constants, anharmonicities, and cross-mode couplings. An unusual cancellation of factors results in the Kr complex (ω'e =72.6 cm−1) having nearly the same metal-rare gas stretching frequency as the Ar complex (ωe=73.9 cm−1). Progressions extending over a significant range of the excited state potential surfaces make it possible to derive the excited state dissociation energies (D'0=755 and 1205 cm−1 for Ar and Kr, respectively). Combination with the red-shifted electronic state origins yields the corresponding ground state dissociation energies (D(large-closed-square)0=275 and 394 cm−1 for Ar and Kr, respectively). Potential energy surfaces are investigated for excited and ground states of both complexes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461545
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Infrared signatures for isomerization and melting in inhomogeneous van der Waals clusters (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6271-6283 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Molecular dynamics simulations are combined with a model for predicting the perturbed infrared spectrum of SF6 in rare gas clusters and used to generate synthetic spectra for a range of cluster isomers and effective temperatures. It is shown that the perturbed infrared spectrum of a vibrationally degenerate chromophore solvated in a cluster can be an incisive tool for determining the number, arrangement, and dynamical state of the solvent particles surrounding the chromophore. The simulations described herein also draw attention to a kind of melting behavior in which the time scale of the "measurement'' directly affects the perception of whether the system is liquidlike or solidlike.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461825
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Dynamic light scattering by aqueous solutions of rodlike fd-virus particles (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6284-6289 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Dynamic light scattering (DLS) measurements on aqueous solutions of rodlike fd-virus particles (length=880 nm, diameter=9 nm) below and above the overlap concentration c*=1 particle/length3 are reported. In samples with screened Coulomb interaction the short-time behavior of the time correlation functions does not show a significant concentration dependence, in contrast to samples at very low ionic strength (strong Coulomb interaction), where the short-time behavior is dominated by the static structure factor S(q). In this case S(q) derived by DLS methods, using an equation that has been proved for interacting spherical particles and weakly interacting rods, is in excellent agreement with S(q) determined by static light scattering (SLS) up to a particle concentration of about 5c*. Above significant deviations are found. At very low ionic strength the existence of a distinct very long tail in the time correlation function as previously reported can be confirmed, but the new experiments suggest that this is due to dust particles and aggregates and not to the interaction between the fd particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461548
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Thermodynamic and kinetic properties of the reaction Cl+O2+M=ClOO+M in the range 160–300 K and 1–1000 bar (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6463-6470 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reaction Cl+O2+M(large-closed-square)ClOO+M was studied by laser flash photolysis in the bath gases M=He, Ar, N2, and O2 over the temperature range 160–300 K and the pressure range 1–1000 bar. UV absorptions of ClOO were monitored, a maximum absorption cross section of σ(248 nm)=3.4×10−17 cm2 was determined. An expression for the equilibrium constant Kp =5.3×10−6 exp(+23.4 kJ mol−1/RT) bar−1 was derived between 180 and 300 K, which, by a third law analysis, yields ΔH(open circle)0 =−20.2±0,2 kJ mol−1. Limiting low pressure rate coefficients for Cl+O2 recombination of k0=[He]8.8×10−34(T/300 K)−3.0, k0=[O2]1.6×10−33(T/300 K)−2.9, k0=[N2]1.4×10−33(T/300 K)−3.9 cm6 s−1 were obtained over the range 160–260 K, as well as k0 (160 K)=[Ar]2.2×10−32 cm6 s−1. Rate constants for the reactions Cl+ClOO→Cl2+O2 or 2ClO, ClOO+ClOO→products, and ClOO+Cl2→Cl2O+ClO were also derived. The recombination Cl+O2(+M)→ClOO(+M) at pressures above 10 bar shows a transition to a high pressure plateau and, at pressures above 200 bar, to diffusion control. It is suggested that, like O+O2(+M)→O3(+M), the reaction is governed by a radical complex mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461543
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Trajectory calculations of ion–molecule momentum transfer rate constants (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6471-6476 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A classical trajectory method is used to calculate thermal energy momentum transfer rate constants for ions in polar and nonpolar gases. The calculations include the consideration of noncapture scattering. For ions in nonpolar gases, the anisotropy of the polarizability and the ion–quadrupole interaction are also included in the calculations. The results show that the noncapture scattering plays an important role in momentum transfer for ions in both polar and nonpolar neutral gases. For ions in anisotropic nonpolar gases, both the anisotropy of the polarizability and the ion–quadrupole potential are important contributors to the momentum transfer rate constants. The theoretical rate constants are in good agreement with a large collection of experimental results. The theoretical results for polar gases are parametrized to an analytical expression which serves as a useful tool for estimating thermal energy ion–polar molecule momentum transfer rate constants. The present theoretical model is more realistic and provides a more accurate estimation of ion–molecule momentum transfer rate constants than previous theoretical treatments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461789
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    The direct photodissociation of ClNO(S1): An exact three-dimensional wave packet analysis (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6496-6507 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present the results of a three-dimensional wave packet study on the photodissociation of ClNO through excitation of the first singlet state S1. The calculations employ an ab initio potential energy surface depending on the Cl–N and N–O bond coordinates and the ClNO bending angle. By expanding the wave packet in terms of the eigenfunctions of the NO rotor, the time-dependent Schrödinger equation is transformed into a coupled set of 60 two-dimensional partial differential equations which are solved by discretization on a grid. The wave packet yields the absorption spectrum and all partial dissociation cross sections for producing the NO fragment in a particular vibrational–rotational state (nj). The photodissociation of ClNO via the S1 state is a relatively fast process and the necessary propagation time is on the order of 50 fs. The calculated data agree well with recent experimental results. For the first time, we can directly compare the wavelength dependence of partial photodissociation cross sections for a single vibrational–rotational fragment state state with experiment. Our results suggest that the photodissociation of ClNO(S1) proceeds mainly adiabatically for the vibrational degree of freedom.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461520
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 11
    Electronic Resource
    Electronic Resource
    Analysis of microviscosity and reaction coordinate concepts in isomerization dynamics described by Kramers' theory (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6508-6523 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this work we have studied the isomerization dynamics of a cyanine dye molecule in solution. The viscosity and temperature dependencies of the isomerization rate have been measured in the series of n-alcohols for three different sizes of the isomerizing group. From these measurements we conclude that the shear viscosity of the solvent is not a good measure of the microscopic friction experienced by the isomerizing groups. The friction is varying in a nonhydrodynamic manner with viscosity, which shows that the relative volume of the isomerizing group and solvent molecules (Vp/Vs) is a critical parameter determining the microscopic friction. When the microscopic friction is calculated using a model for molecular rotational relaxation proposed by Dote, Kievelson, and Schwartz [J. Phys. Chem. 85, 2169 (1981)], good fits to Kramers' equation is obtained. Similar models for microscopic rotational and translational friction combined with Kramers' equation also yield an apparent improvement over the hydrodynamic Kramers description. The measurements also show that the non-Kramers behavior of the reaction rates have a more complex origin than the (Vp/Vs) dependence of the microscopic friction, that possibly can be traced back to a more general failure of the hydrodynamic description of friction (frequency dependent friction), or to a temperature and solvent dependence of the potential surface parameters. The results also suggest that the detailed nature of the reaction coordinate plays an important role in determining the detailed viscosity dependence of the isomerization. Thus a reactive motion mainly experiencing rotational friction is much more sensitive to the molecular size and free-volume effects, than is the isomerization controlled by translational friction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461521
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 12
    Electronic Resource
    Electronic Resource
    Time-dependent treatment of vibrational predissociation within the golden rule approximation (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6449-6455 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The time-dependent formulation for vibrational predissociation of weakly bound complexes within the golden rule treatment is presented. The quantum wave packet propagation in this formulation eliminates the difficulty of strenuous long time propagation of the full wave function due to long-lived resonance which occurs in the more exact time-dependent treatment. As a result, the new time-dependent treatment of vibrational predissociation essentially parallels that of direct photodissociation and therefore requires only short time propagation of the wave function. The wave packet propagation is efficiently carried out in the interaction picture and numerical calculations of rotational state distributions and the total decay width are presented for vibrational predissociation of HeCl2. Correct rotational state distribution can be obtained with only a few time propagation steps owing to the use of large step size allowed in the interaction picture. Our approach provides an efficient method for the calculation of vibrational predissociation for more complex systems such as those with more than three atoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461565
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 13
    Electronic Resource
    Electronic Resource
    Diffusion and reaction in heterogeneous media: Pore size distribution, relaxation times, and mean survival time (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6477-6489 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Diffusion and reaction in heterogeneous media plays an important role in a variety of processes arising in the physical and biological sciences. The determination of the relaxation times Tn (n=1,2,...) and the mean survival time τ is considered for diffusion and reaction among partially absorbing traps with dimensionless surface rate constant κ¯. The limits κ¯=∞ and κ¯=0 correspond to the diffusion-controlled case (i.e., perfect absorbers) and reaction-controlled case (i.e., perfect reflectors), respectively. Rigorous lower bounds on the principal (or largest) relaxation time T1 and mean survival time τ for arbitrary κ¯ are derived in terms of the pore size distribution P(δ). Here P(δ)dδ is the probability that a randomly chosen point in the pore region lies at a distance δ and δ+dδ from the nearest point on the pore–trap interface. The aforementioned moments and hence the bounds on T1 and τ are evaluated for distributions of interpenetrable spherical traps. The length scales 〈δ〉 and 〈δ2〉1/2, under certain conditions, can yield useful information about the times T1 and τ, underscoring the importance of experimentally measuring or theoretically determining the pore size distribution P(δ). Moreover, rigorous relations between the relaxation times Tn and the mean survival time are proved. One states that τ is a certain weighted sum over the Tn, while another bounds τ from above and below in terms of the principal relaxation time T1. Consequences of these relationships are examined for diffusion interior and exterior to distributions of spheres. Finally, we note the connection between the times T1 and τ and the fluid permeability for flow through porous media, in light of a previously proved theorem, and nuclear magnetic resonance (NMR) relaxation in fluid-saturated porous media.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461519
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 14
    Electronic Resource
    Electronic Resource
    C˜→A˜ emission in H2O following two-photon excitation: Dissociation dynamics in the A˜ state for different initial states (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6536-6543 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: C˜→A˜ emission spectra of the water molecule have been observed following two-photon excitation to various vibrational levels of the C˜(1B1) electronic state. Photodissociation dynamics on the A˜(1B1) state potential energy surface were probed through the C˜→A˜ emission spectra. The different spectra correspond to photodissociation trajectories in the A˜ state starting with a variety of initial conditions. Time-dependent quantum mechanical simulations of the emission spectra show good agreement with the experimental data and provide further insight into the dissociation dynamics on the A˜ state surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461523
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 15
    Electronic Resource
    Electronic Resource
    Quasidiabatic states from ab initio calculations by block diagonalization of the electronic Hamiltonian: Use of frozen orbitals (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6668-6680 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The construction of quasidiabatic states is of theoretical and practical relevance in treating systems that exhibit strong nonadiabatic interactions. In the present work the implementation of the recently proposed method of block diagonalization of the electronic Hamiltonian in CI-type calculations, both theoretically and in practical calculations is investigated in detail. It is shown that the use of shifted or frozen molecular orbitals in the calculation of the adiabatic potential energy surfaces provides the most appropriate N-electron wave functions for applying the block diagonalization procedure. Freezing means to conserve the composition of the molecular orbitals at some chosen geometry, i.e., to have their coefficients unchanged with respect to the atomic orbitals with varying nuclear geometry. The use of the frozen orbitals and block diagonalization of the resulting CI matrix yields a method that treats orbital coupling and configurational interaction efficiently at the same time, leading to quasidiabatic states. Due to the mathematical simplicity of the method and to the fact, that no derivative couplings are needed during the calculations, the additional computational cost is negligible. Application to the ethylene dication illustrates the successful performance of the proposed method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461537
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 16
    Electronic Resource
    Electronic Resource
    Effect of the band degeneracy on the electronic structure: Application to the aluminum clusters (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6734-6737 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Using a modified Gutzwiller technique, the effect of the band degeneracy on the electronic structure of dimer has been carried out. Aluminium clusters Aln (n≤6) have been investigated: The present calculation is in agreement with ab initio calculations; a singlet to triplet state transition is occurring for n=4.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461511
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 17
    Electronic Resource
    Electronic Resource
    Hydrogen bonding and the static dielectric constant in liquid water (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6762-6769 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The static dielectric constants of several models for water are compared. These models have in common that they all give a good description of the energetics and structure of the hydrogen bonding in the liquid. Despite this similarity, the average molecular dipole moments vary over a range of 50% and the dielectric constants can differ by as much as a factor of 6. This observation verifies that the average dipole moment is a crucial parameter for the dielectric properties. On the other hand, this quantity seems of less importance for the stability of the hydrogen bonded network, which is largely determined by the details of the electrostatic and atom–atom interactions at short range. Applying this analysis we construct a polarizable model for liquid water with an average dipole moment of 2.6 D and a dielectric constant of 85. The structure and self-diffusion coefficient are in good agreement with experiment, and the value of the dimer binding energy in the gas phase is also acceptable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461515
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 18
    Electronic Resource
    Electronic Resource
    Thermodynamics and structure of the primitive model near its gas–liquid transition (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6784-6791 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The hypernetted-chain/mean spherical approximation (HNC/MSA) is employed to calculate the thermodynamic properties of the restricted primitive model (symmetric binary mixture of charged hard spheres) in the low density–high coupling region, where the gas–liquid phase transition is located. The spinodal curve is calculated from the virial and the compressibility equations. The HNC/MSA total correlation function does not show long-range behavior as the spinodal curve is approached. This is due to the hybrid nature of this approximation. However, a consistent HNC/MSA total correlation function is defined which does show the expected long-range behavior. This long-range behavior is found to be related to the phenomenon of ionic clustering, in accordance with previous studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461516
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 19
    Electronic Resource
    Electronic Resource
    Mean spherical approximation algorithm for multicomponent multi-Yukawa fluid mixtures: Study of vapor–liquid, liquid–liquid, and fluid–glass transitions (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6806-6837 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An efficient algorithm is given to find the Blum and Høye mean spherical approximation (MSA) solution for mixtures of hard-core fluids with multi-Yukawa interactions. The initial estimation of the variables is based on the asymptotic high-temperature behavior of the fluid. From this initial estimate only a few Newton–Raphson iterations are required to reach the final solution. The algorithm consistently yields the unique thermodynamically stable solution, whenever it exists, i.e., whenever the fluid appears as a single, homogeneous phase. For conditions in which no single phase can appear, the algorithm will declare the absence of solutions or, less often, produce thermodynamically unstable solutions. A simple criterion reveals the instability of those solutions. Furthermore, this Yukawa-MSA algorithm can be used in a most simple way to estimate the onset of thermodynamic instability and to predict the nature of the resulting phase separation (whether vapor–liquid or liquid–liquid). Specific results are presented for two binary multi-Yukawa mixtures. For both mixtures, the Yukawa interaction parameters were adjusted to fit, beyond the hard-core diameters σ, Lennard-Jones potentials. Therefore the potentials studied, although strictly negative, included a significant repulsion interval. The characteristics of the first mixture were chosen to produce a nearly ideal solution, while those of the second mixture favored strong deviations from ideality. The MSA algorithm was able to reflect correctly their molecular characteristics into the appropriate macroscopic behavior, reproducing not only vapor–liquid equilibrium but also liquid–liquid separations. Finally, the high-density limit of the fluid phase was determined by requiring the radial distribution function to be non-negative. A case is made for interpreting that limit as the fluid–glass transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461493
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 20
    Electronic Resource
    Electronic Resource
    The quantum mechanics of clusters: The low-temperature equilibrium and dynamical behavior of rare-gas systems (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6658-6667 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We consider in the present paper the quantum-mechanical effects on the equilibrium and dynamical behavior of low-temperature rare-gas clusters. Using a combination of ground-state and finite-temperature Monte Carlo methods, we examine the properties of small (2–7 particles) neon clusters. We find that the magnitude of the equilibrium quantum-mechanical effects in these systems is significant. The present studies also suggest that the low-temperature dynamics of these rare-gas systems is appreciably nonclassical.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461536
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 21
    Electronic Resource
    Electronic Resource
    Exact perturbation treatment of the basis set superposition correction (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6705-6711 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: It is shown that a complete removal of the basis set superposition effect on the interaction properties of a composite system can be understood in terms of constraints imposed on its wave function. This interpretation of the basis set superposition effect is used to build variation methods which account for the constraints imposed by the incompleteness of available solutions for the constituent subsystems. A perturbation analysis of the resulting constrained equations provides an exact method for the evaluation of the basis set superposition contribution to interaction properties. The corresponding perturbation correction is explicitly evaluated for the Hartree–Fock approximation and discussed at the level of different correlated methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461540
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 22
    Electronic Resource
    Electronic Resource
    Time-resolved observation of excitation hopping between two anthryl moieties attached to both ends of polystyrene chains (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6877-6884 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Excitation hopping between two 9-anthryl moieties attached to both ends of polystyrene chains with various molecular weights has been explored by picosecond time-resolved fluorescence anisotropy measurements. The measurements were performed at 77 K in the rigid matrix of 2-methyltetrahydrofuran (MTHF) or methylcyclohexane (MCH) in order to exclude the effect of rotational diffusion of the chromophores to the fluorescence anisotropy. The hopping behavior was found to be very sensitive to such factors as molecular weight (Mn), solvent, and concentration of the samples. In MTHF (good solvent), the excitation hopping was only observed for a sample with Mn∼104; on the other hand, it occurred unequivocally for samples with Mn∼105 in MCH (poor solvent), as evidenced by a clear decay of the fluorescence anisotropy, r(t). Furthermore, the excitation hopping was an intramolecular event only at very low concentration (∼10−7 M based on polymer chain), and at 10−6 M, an intermolecular excitation hopping was observed. Such sharp dependence of the excitation hopping on the concentration was interpreted in terms of chain collapse at low temperature. Simulation of r(t) was performed on the basis of Förster mechanism and Gaussian chain statistics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461499
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 23
    Electronic Resource
    Electronic Resource
    The dynamics of surface rearrangements in Si adatom diffusion on the Si{100}(2×1) surface (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6885-6891 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Si adatom adsorption and diffusion on the fully relaxed Si{100}(2×1) surface is studied by a combination of molecular dynamics simulations with Tersoff's potential for the Si interactions, a simplified transition state theory of Voter and lattice gas simulations. Six local minima for adsorption are found on the surface and the activation energies between each are determined. The Arrhenius behavior for the macroscopic diffusion is found to be D=5.67×10−3 exp(−0.75 eV/kT) cm2/s. In addition, it is found that the adatom diffusion is strongly anisotropic in nature and the direction of easy diffusion is perpendicular to the dimers (i.e., parallel to the dimer rows) of the original surface. The minimum energy path for the diffusion is found to be activated by the local unreconstruction (dimer opening) of the otherwise fully reconstructed surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461500
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 24
    Electronic Resource
    Electronic Resource
    Adsorbate–adsorbate interactions for PF3 chemisorbed on Pt(111) (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6962-6971 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: To gain a better understanding of adsorbate–adsorbate interactions for chemisorbed polyatomic molecules we have measured the coverage and temperature dependence of the PF3 symmetric bend and P—F symmetric stretch fundamentals of PF3 chemisorbed on Pt(111). The two bands exhibit distinctly different responses to lateral interactions. The P—F stretch shifts from 901 to 951 cm−1 with increasing coverage and at intermediate coverages splits into two components separated by 5–13 cm−1 with a relative intensity which is strongly temperature dependent. By contrast, the symmetric bend shifts from 541 to 562 cm−1 and remains as a single band under all conditions. The symmetric bend displays only a slight asymmetry under conditions where the P—F stretch is split into two components. The different behavior of the two bands along with other considerations indicate that both coupling and chemical shifts determine the P—F stretch frequency for PF3 chemisorbed on Pt(111).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461507
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 25
    Electronic Resource
    Electronic Resource
    Microscopic expressions for the rigidity constants of a simple liquid–vapor interface (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6986-6988 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present microscopic equations for the rigidity constants of a simple liquid–vapor interface. These expressions are analogous to the Kirkwood–Buff formula for the surface tension. The rigidity constants are calculated using an approximate expression for the density auto correlation function in the interface near the critical point. This results in k=0.631 kBTc and k=0.239 kBTc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461509
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 26
    Electronic Resource
    Electronic Resource
    Structure-constrained anionic polymerization in hydrogen-bonded acrylonitrile clusters (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6989-6992 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Electron attachment processes involving acrylonitrile (AN) clusters and high-Rydberg Kr atoms (Kr**) were investigated by mass spectrometry. A particular abundance of cluster fragment anions, [(AN)n−H]−, [(AN)n−H2]−, and [(AN)n−H2−HCN]− with N=3,6,9,..., was explained by formation of a trimeric core ion xolvated with stable AN trimer units as a result of anionic polymerization of three AN molecules in a ring geometry in the parent cluster.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461510
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 27
    Electronic Resource
    Electronic Resource
    Rotational tunneling of methane on MgO surfaces: A neutron scattering study (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6997-7000 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: High-resolution inelastic neutron scattering was used to investigate the rotational tunneling of methane molecules in a (large-closed-square)×(large-closed-square)R45° commensurate, square-lattice–solid monolayer adsorbed on MgO (100) surfaces. Good matches to the observed transition energies were obtained using potential functions with C2v symmetry, suggesting that the preferred orientation of the molecule is the dipod-down configuration with two opposite edges of the H-atom tetrahedron parallel to the surface plane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461044
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 28
    Electronic Resource
    Electronic Resource
    Paramagnetism of high nuclearity metal cluster compounds as derived from local density functional calculations (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 7004-7007 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electronic structure of high nuclearity carbonylated Ni clusters [Ni32C6(CO)32]n− and [Ni44(CO)48]n− (n=0–6) has been investigated by means of all-electron calculations within the local density functional approach. The transition from the molecular to the metallic state was studied by determining the magnetic properties of bare and carbonylated clusters. The appearance of the metallic magnetic behavior is connected with the presence of metal atoms with bulklike coordination. The effect of interstitial impurity atoms in quenching the magnetic moment is also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461045
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 29
    Electronic Resource
    Electronic Resource
    A classical, simulated, microscopic Poisson process (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 7013-7014 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: It is shown that both the full simulation and the generalized Langevin dynamics simulation π flips in a two-dimensional array of interacting benzene rings [P. Romiszowski and R. Yaris, J. Chem. Phys. XX, xxxx (1991)] satisfy Poisson statistics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461048
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 30
    Electronic Resource
    Electronic Resource
    Low-frequency Raman spectra of guanosine and nucleotides in ordered states: Origin of the lowest-frequency mode (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5519-5523 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Raman spectra of self-associates of guanosine were investigated in the 5–200 cm−1 region together with crystals of guanosine⋅2H2O, Na2⋅5'–UMP⋅7H2O, Na2⋅5'–GMP⋅7H2O, Na2⋅5'–CMP⋅8H2O, Na2⋅5'–dGMP⋅4H2O, and Na2⋅ATP⋅3H2O, to clarify the origin of the lowest Raman active mode of deoxyribonucleic nucleic acid (DNA). When the bases stack well to form a column, as in guanosine self-associates and crystals of guanosine and adenosine triphosphate (ATP), the spectral patterns are similar to that of DNA. The lowest-frequency bands are sharp and isolated from other bands. The result suggests that the origin of the lowest-frequency mode of DNA is assigned to the motion of bases stacked in a column. Guanosine has no phosphate groups, and ATP has no hydrogen bonds between bases in the crystal state. Therefore, neither hydrogen bonds between bases nor phosphate groups are necessary for the existence of this mode.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461625
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 31
    Electronic Resource
    Electronic Resource
    The range dependence of fluorescence anisotropy in molecular energy transfer (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5513-5518 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In the theory of excitation energy transfer it is generally considered that species initially excited by photoabsorption transfer their energy to other molecules by two distinct mechanisms, known as radiative and radiationless energy transfer. Recently it has been shown that the two mechanisms for energy transfer are in fact indistinguishable, each being the asymptotic limit of a unified mechanism involving virtual photon coupling. The familiar R−6 dependence associated with Förster radiationless transfer is the short-range limit, while over longer distances retardation effects modify the radial dependence to R−2, and the result is the classical radiative transfer law. For radiationless energy transfer, wide use is made of Galanin's result concerning fluorescence depolarization losses due to single-step transfer. Here Galanin's work is extended to obtain a general formula for the residual fluorescence anisotropy following energy transfer over arbitrary intermolecular distances. Hence a connection is established with the depolarization associated with reabsorption. In particular, it is shown that the anisotropy increases significantly from its initially low value over distances considerably less than those normally associated with radiative energy transfer. The necessary criteria for experimental identification of the transition from radiationless to radiative character are described, and model systems for their realization are considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461624
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 32
    Electronic Resource
    Electronic Resource
    Infrared spectra of water. I. Effect of temperature and of H/D isotopic dilution (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5565-5573 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The implementation of a cell operating with the technique of Attenuated Total Reflection (ATR) enabled us to obtain good quality IR spectra of water for the whole region above 750 cm−1 (which is the limit of the effect of the cutoff wave number of the crystal) and up to 5000 cm−1. ATR spectra have been recorded as a function of temperature ranging from −5 °C to 80 °C and of H/D molar concentration c(0〈c〈1). They have been transformed into spectra in ε‘, using the Bertie–Eysel iteration procedure. In this paper evolutions of these spectra in ε‘ upon variations of these two parameters c and T are investigated and analyzed. It is shown that any experimental spectrum in ε‘ of a mixture of normal and heavy water is a superposition of three spectra due to pure H2O, pure D2O, and a spectrum that is only slightly dependent upon isotopic concentration c and is consequently mainly due to HDO. Analysis of this slight dependence upon c allows precise conclusions concerning vibrational interactions for both bending bands δ and stretching bands νs to be reached. Evolution of spectra with temperature unambiguously shows that all spectra at temperature T may be decomposed into a low temperature spectrum and a high temperature spectrum. The coefficient defining this decomposition [Eqs. (11) and (14)] displays a quadratic variation with T. It is the same for H2O, D2O, and HDO within the precision of the experiment. A low temperature spectrum corresponding to a (slightly distorted) H-bond network with no other defects, as well as a high temperature spectrum due to "defects'' cannot, however, be determined without any further assumption. Limits for values of the concentration of defects α(T) may nevertheless be established.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461630
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 33
    Electronic Resource
    Electronic Resource
    Coherent anti-Stokes Raman spectroscopy of shock-compressed liquid carbon monoxide (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5603-5608 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrational spectra of liquid carbon monoxide shock compressed to several high pressure/high temperature states were recorded using single-pulse multiplex coherent anti-Stokes Raman scattering. Vibrational frequencies, third-order suceptibility ratios, and linewidths are reported for the fundamental and first excited-state transition. The observed vibrational frequency shift with shock pressure was substantially less than that observed previously in nitrogen, implying a significant difference in the details of their inter- and intramolecular potentials. The transition intensity and linewidth data suggest that thermal equilibrium of the vibrational levels is attained in less than 10 ns at these shock pressures, and the vibrational temperatures obtained are comparable to calculated equation-of-state temperatures. The measured linewidths suggest that the vibrational dephasing time decreased to ∼2 ps at our highest pressure shock state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461634
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 34
    Electronic Resource
    Electronic Resource
    Spectroscopic studies of jet-cooled AgAu and Au2 (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5646-5659 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Resonant two-photon ionization spectroscopy has been applied to the jet-cooled Au2 and AgAu molecules. Three new band systems of Au2 and two new systems of the poorly characterized AgAu molecule have been observed. Excited state lifetime measurements have been made, and assignments of the excited states are suggested. For Au2 the a 3Σ+1u←X 1Σ+g transition has been detected, and vibrational levels of the a 3Σ+1u state have been observed up to v'=33, which lies only 120 cm−1 below the convergence limit of the system. This allows a precise confirmation of previous high temperature Knudsen effusion measurements of the bond strength of Au2 as D00(Au2)=2.290±0.008 eV. In addition, the excited states of Au2 of 0+u symmetry are shown to have significantly shorter fluorescence lifetimes than the 1u states, and this is explained as resulting from an admixture of Au+Au− ion pair character in these Ω'=0+u states. The ionization potential of Au2 has been bracketed as IP(Au2)=9.20±0.21 eV, which may be combined with the values of D00(Au2) and IP(Au) to provide the dissociation energy of the Au+2 ion as D00(Au+2)=2.32±0.21 eV. Detailed comparisons with theoretical results are made for Au2, and assignments of the A and B states of AgAu to Ω'=0+ and Ω'=1, respectively, are proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461639
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 35
    Electronic Resource
    Electronic Resource
    The vibrational spectrum and rotational constants of difluoroethyne FC 3/4 CF. Matrix and high resolution infrared studies and ab initio calculations (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5660-5669 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Infrared spectra of the short-lived difluoroethyne molecule have been recorded in neon and argon matrices between 200 and 5000 cm−1. Fourier transform infrared spectra with a resolution of 0.004 cm−1 have been measured in the gas phase around 1350 cm−1 (ν3, ν2+ν4+ν5, hot bands) and 2150 cm−1 (ν2+ν3, ν1−ν5, hot bands). The high resolution study yields rotational parameters of the ground and all singly excited vibrational states. The interpretation of the experimental data has been guided by ab initio calculations at the SCF (self-consistent-field) level and the correlated MP2 level (Moller–Plesset second order perturbation theory) employing three different large basis sets. The theoretical calculations provide the SCF and MP2 harmonic fields as well as the SCF anharmonic force field of FCCF. The agreement between the available theoretical and experimental results is generally quite good, with the exception of the spectroscopic constants involving the trans-bending mode ν4 where more theoretical work is required. The combined use of theoretical and experimental information leads to an estimate of the equilibrium structure [D∞h, re(CC)=1.1865 A(ring), re(CF)=1.2832 A(ring)] and to recommended "best'' values for the wave numbers of all fundamental vibrations based on the matrix and high resolution infrared data and some ab initio anharmonicity constants. The present study demonstrates the advantages of a combined theoretical and experimental approach to the spectroscopy of short-lived molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461640
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 36
    Electronic Resource
    Electronic Resource
    Evolution of the orientational and internal-state distribution of molecules in an expanding jet (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5719-5731 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report experiments on the internal state distribution and angular momentum alignment in an expanding jet of Na2 molecules seeded in Ar. The results show that even at a distance of one nozzle diameter from the nozzle exit, the distribution function is already far from equilibrium. It is found that the deviation from equilibrium can be expressed in a polynomial in the total internal energy of the molecules. This result is very analogous to the outcome of a first order Chapman–Enskog treatment for molecules with internal states. The transition to molecular flow marks the breakdown of the simple relationship mentioned above. This points to the fact that data taken far away from the nozzle are by themselves of limited value for a test of calculated distributions starting from nozzle conditions. Further we present measurements of alignment for two rovibrational states of Na2 molecules. Far downstream the nozzle the results are in agreement with previous experiments in molecular beams. In the vicinity of the nozzle reorienting collisions of excited-state molecules play an important role. It appears that these collisions strongly depend on the rotational state of the molecules: the cross sections are inversely proportional to J'2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461621
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 37
    Electronic Resource
    Electronic Resource
    Picosecond polarization-selective transient grating experiments in sodium-seeded flames (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5775-5784 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Polarization-selective transient grating experiments have been used to study the subnanosecond time scale dynamics of several sodium-seeded, premixed flames. Intensity gratings (in which both excitation beams are of the same polarization) were used to determine excited-state quenching collision rates, while polarization gratings (in which the excitation beams are cross polarized) were used to measure Na diffusion constants and the rates of Na ground state magnetic sublevel population scattering collisions. In addition, the rates of scattering between the 3P1/2 and 3P3/2 excited state levels were measured using an excited state probing scheme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461599
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 38
    Electronic Resource
    Electronic Resource
    Experimental determination and calculation of the collision relaxation rates in the 5 2P1/2 and 5 2P3/2 levels of atomic iodine (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5790-5798 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Pressure broadening of the hyperfine lines of the 2P1/2 –2P3/2 atomic iodine transition is analyzed from the emission line shapes. Collisions with Ar and O2 in the 0–100 Torr range were examined as well as pressure broadening due to I2 in the 0–15 Torr range. Pressure broadening coefficients α were determined: α (O2)=4.8 (3) MHz/Torr and α (Ar)=3.6 (3) MHz/Torr. In the case of I2, α (I2) is estimated to be (35±10) MHz/Torr in the 0–5 Torr range. In addition, pressure broadening coefficients were calculated using the impact approximation. In this approximation relaxation cross sections are calculated between hyperfine levels of the I atom. Estimates of the relaxation rates between the hyperfine levels of I(2P3/2) and I(2P1/2) are deduced from these results, for both elastic and inelastic processes. Experimental and theoretical results are in reasonable agreement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461601
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 39
    Electronic Resource
    Electronic Resource
    Predominant decay channel for superexcited organic molecules (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5846-5852 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Photoabsorption and photoionization cross sections of organic molecules are systematically compared for elucidating relation between superexcitation and ionization. The cross sections examined are of alkenes, alkanes, alcohols, and ethers in the energy range of about 2 eV above the first ionization potential. Although the photoabsorption cross sections are much different from one another, the photoionization cross sections are similar in each molecular group. This result indicates that ions are formed only through direct photoionization and most of superexcited molecules dissociate to neutral fragments. Ionization efficiency curves are calculated under the assumption of no autoionization, and they well reproduce the observed ionization curves, which mainly depend on energy difference between the first and second ionization potentials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461605
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 40
    Electronic Resource
    Electronic Resource
    Theoretical study of redistribution of light in Ca–He collisions (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5861-5872 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The quantum theory of atomic collisions in the presence of a weak radiation field is used to describe the process of redistribution of light in Ca–He collisions. This work is devoted to the simulation of the recent experiment of Lin and co-workers [J. Chem. Phys. 89, 4771 (1988)] in which, the absorption profile of the (4s2 1S→4s5p 1P) transition and the dependence on the detuning of the spin-changing (4s5p 1P→4s5p 3P) transition were determined. Close-coupled calculations are carried out, based on model interaction potentials for the ground and the excited states of the Ca–He system. The calculated absorption profile for the production of Ca atom in the (4s5p 1,3P) states is in qualitative agreement with the experimental results. The blue wing/red wing asymmetry in the relative transfer to the 3P state, is interpreted in terms of flux transfer among the molecular states, which occurs when the Ca atom is approached by the closed-shell partner.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461607
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 41
    Electronic Resource
    Electronic Resource
    The reduced multiplication scheme of the Rys quadrature and new recurrence relations for auxiliary function based two-electron integral evaluation (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5889-5897 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reduced multiplication scheme of the Rys quadrature is presented. The method is based on new ways in which the Rys quadrature can be developed if it is implemented together with the transfer equation applied to the contracted integrals. In parallel to the new scheme of the Rys quadrature improvements are suggested to the auxiliary function based algorithms. The two new methods have very favorable theoretical floating point operation (FLOP) counts as compared to other methods. It is noted that the only significant difference in performance of the two new methods is due to the vectorizability of the presented algorithms. In order to exhibit this, both methods were implemented in the integral program seward. Timings are presented for comparisons with other implemenations. Finally, it is demonstrated how the transfer equation in connection with the use of spherical harmonic Gaussians offers a very attractive path to compute the two-electron integrals of such basis functions. It is demonstrated both theoretically and with actual performance that the use of spherical harmonic Gaussians offers a clear advantage over the traditional evaluation of the two-electron integrals in the Cartesian Gaussian basis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461610
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 42
    Electronic Resource
    Electronic Resource
    A generalized Heitler–London theory of the chemical bond in H+2 (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5918-5929 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The perturbation theory for the total energies of the 1sσg and 2pσu states of H+2 is reformulated in a manner which avoids problems resulting from symmetrization. First a new set of localized wave functions are defined and calculated from polarization perturbation theory. After symmetrization of these wave functions, a generalized Heitler–London energy, which can be expanded to all orders, is obtained. In second order the result agrees with the Murrell–Shaw Musher–Amos expression. An expansion of the expectation value of the energy is also carried out and provides similar results. Many symmetry-adapted perturbation results are obtained simply and directly from the present localized wave-function approach. The present theory suggests a novel interpretation of the terms contributing to the total potential energy and helps to rearrange them to give improved results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461613
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 43
    Electronic Resource
    Electronic Resource
    Comparison between molecular dynamics simulations and the Smoluchowski theory of reactions in a hard-sphere liquid (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5948-5952 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Molecular dynamics simulations of the kinetics of a model of the reaction A+B→B in a dense hard-sphere liquid are compared with the predictions of the Smoluchowski approach to diffusion-influenced reactions. The theory employs the radiation boundary condition at contact with an intrinsic rate constant determined by the low-density collision frequency and the potential of mean force determined by the pair distribution function. Hydrodynamic interactions are ignored and the relative diffusion coefficient is taken as twice the self-diffusion constant. Considering the lack of free parameters and the many-body nature of the problem, the agreement between theory and simulations is surprisingly good over a wide range of B concentrations. Of particular interest is that the above theory provides an exact description of the kinetics at short times.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461616
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 44
    Electronic Resource
    Electronic Resource
    Dielectric relaxation dynamics of water and methanol solutions associated with the ionization of N,N-dimethylaniline: Theoretical analyses (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5966-5982 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The solvation dynamics associated with the ionization of N,N-dimethylaniline (DMA) in water and methanol solutions has been studied theoretically. Potential energy surfaces of DMA and DMA+ were computed by ab initio molecular orbital (MO) methods. Intermolecular pair potential functions between DMA and H2O were developed with the aid of the electron distributions of DMA and H2O and the results of MO calculations for the DMA–H2O system. Potential functions between DMA and MeOH were also determined empirically using the parameters for DMA–H2O interaction. Equilibrium and nonequilibrium molecular dynamics calculations were carried out for the DMA–water and DMA–methanol solutions. The simulation results were analyzed comparing two solvents in order to obtain a realistic molecular model for the solvation dynamics of DMA in polar solvents. The solvation coordinate was defined by the potential energy difference between neutral and cation states and free energy curves along it were constructed using the umbrella sampling method. They were found to be well described by parabolas and nonlinear effects such as the dielectric saturation were not observed. The fluctuation–dissipation relation was also examined. It was found that the present systems follow the linear response to a reasonable approximation. In order to provide a kinematic foundation for the choice of the solvation coordinate, the generalized Langevin equation (GLE) for the motion along the solvation coordinate is derived utilizing the reaction path model originally developed to describe photochemical processes in the gas phase. The mechanism of the dielectric relaxation dynamics was discussed on the basis of the quantities in the GLE deduced from the molecular dynamics (MD) calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461618
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 45
    Electronic Resource
    Electronic Resource
    Interaction of monovalent ions with the water liquid–vapor interface: A molecular dynamics study (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6005-6013 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Results of molecular dynamics studies on the ions Na+,F−, and Cl− near the water liquid–vapor interface are reported. The free energies required to move the ions to the interface are presented and shown to depend on the sign of the ionic charge, and not the size of the ion. F− and Cl− can approach to within 2 molecular layers of the interface without incurring a significant change in free energy, while it costs about 2.5 kcal/mole to move Na+ this same distance. The free energy differences between the cation and the anions arise from the interaction of the ions with the water molecules in the interfacial region. These water molecules are oriented with a slight preference for their molecular dipoles to point toward the liquid. Thus, the anions approaching the interface disrupt the water structure less than does the cation. The calculated free energy curves were compared with predictions of simple dielectric models. It was shown that these models do not provide a good description of ions at the water surface. The ions were found to retain their first solvation shells at the interface. The anions also retain part of their second solvation shells, while Na+ does not. As a result, a larger bulge in the water surface is observed above the anions than above Na+. The lateral mobilities of the ions increase at the interface, in qualitative agreement with predictions of hydrodynamic models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461592
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 46
    Electronic Resource
    Electronic Resource
    Eigenstates of a quantum-mechanical particle on a topologically disordered surface: H(D) atom physisorbed on an amorphous ice cluster (H2O)115 (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6026-6038 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We examined energy levels and stationary states of a quantum-mechanical particle adsorbed on a rough and disordered surface. The specific system examined consists of an H atom (or a D atom) adsorbed on an amorphous ice cluster (H2O)115. Two kinds of stationary states of the adsorbate particle were obtained: states localized in cavities on the cluster surface, and states occupying corridors of low potential energy present on the cluster surface. Zero-point energy effects were found to be very significant; thus the ordering of ground state energies in the different cavities does not follow at all the ordering of minimum potential energies in the cavities. Significant localization was demonstrated of the calculated eigenstates within small portions of connected energetically accessible regions on the cluster surface. The localization seems to be associated with disorder in the three-dimensional potential energy surface, which includes strongly varying well depth, and sharp turns in potential contours. Phase matching of the adsorbate wave function is not easily achieved in the different parts of the potential well, the result being localization of the eigenstates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461571
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 47
    Electronic Resource
    Electronic Resource
    Conformations of a polymer boxed into a corner: Role of excluded volume (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6112-6123 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The influence of surface constraints on the conformations of a flexible polymer are investigated. The polymer is modeled as a Gaussian chain, and the influence of repulsive polymer–polymer excluded volume interactions is investigated using renormalization group methods. Various measures of the polymer mean dimensions are computed for chains terminally attached to mutually orthogonal surfaces and for a wide range of polymer excluded volume interactions. Two limiting cases of the polymer–surface interaction are considered—the absorbing boundary condition corresponding to a "repelling'' surface and the reflecting boundary condition associated with the "adsorption theta point,'' where surface attractions fall just short of adsorbing the polymer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461580
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 48
    Electronic Resource
    Electronic Resource
    The relaxation spectrum and diffusion in concentrated systems of spherical particles (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6124-6135 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The viscoelastic properties of a concentrated monodisperse latex of polyvinylidene fluoride coated by a monolayer of the surfactant C12E6 has been examined as a function of volume fraction. This system shows solidlike behavior in the linear viscoelastic region. A model is developed to describe number density fluctuations in the sample in terms of the colloid pair interaction energy. This is used to determine the relaxation spectrum and is then compared with experimental data. Excellent agreement is found between the model and the measured stress relaxation response. This model has been compared to published data on polystyrene latex and has also shown excellent agreement. A tracer diffusion coefficient is calculated to illustrate that the dynamic processes controlling relaxation are slow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461581
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 49
    Electronic Resource
    Electronic Resource
    The mechanism of kinetic oscillations in catalytic oxidation of CO on Pt(210) (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6162-6170 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Under isothermal conditions at low pressure (10−4 Torr), the catalytic oxidation of CO on a Pt(210) surface exhibits kinetic oscillations which have been investigated using Video-LEED, measurement of the CO2 production rate and the variation of work function. An induction period of ∼30 to 60 min, which has been shown to be due to a facetting of the surface exists before the appearance of kinetic oscillations. If reaction conditions are chosen which correspond to the high rate branch of Langmuir Hinshelwood kinetics, the Pt(210) surface facets into (310) and (110) orientations. The facetting process is associated with a decrease in catalytic activity caused by a lowering of the oxygen sticking coefficient. In situ LEED experiments demonstrated that the oscillations in the reaction rate are associated with periodic intensity variations of the half-order LEED beams belonging to (110) facets. Thus, the oscillations appear to be driven by the CO-induced 1×1(arrow-right-and-left)1×2 phase transition on (110) facets in the same way as has been verified for the system Pt(110)/CO+O2. The involvement of a facetting process explains the characteristic properties of kinetic oscillations on Pt(210) such as the relatively low high-temperature limit of ≈500 K, the existence of an induction period and the period length which is on the order of minutes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461584
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 50
    Electronic Resource
    Electronic Resource
    Velocity selective rotational rainbows for normal incidence/normal detection gas–surface scattering (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6178-6180 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Velocity selected rotational state distributions of N2 molecules scattered from Ag(111) have been measured. These measurements have been made at normal incidence and normal detection for incident energies of 0.25 and 0.75 eV. This new technique allows us to rapidly study the cross correlation between the exit rotational state and its velocity distribution. A pronounced difference between the rotational distributions of fast and slow scattered molecules is observed, and this difference is much more pronounced for high incident kinetic energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461587
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 51
    Electronic Resource
    Electronic Resource
    Absolute measurements of photoabsorption and photoionization cross sections of disilane in the 13–40 eV region (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6188-6189 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461593
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 52
    Electronic Resource
    Electronic Resource
    Comment on: Adsorption and diffusion at rough surfaces. A comparison of statistical mechanics, molecular dynamics, and kinetic theory (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6194-6195 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461595
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 53
    Electronic Resource
    Electronic Resource
    Numerical simulation of rodlike polymers in a uniaxial extensional flow: The distribution-function version versus the order-parameter version of Doi's theory (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6042-6049 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The molecular theory of nematic liquid crystals, proposed by Doi in 1981, exists in two versions: the original kinetic equation written in terms of the orientational distribution function and an averaged approximation of the original kinetic equation written in terms of the order parameter tensor. In this study, the two versions, as well as a third (hybrid) approach by Edwards and Beris (1989), are compared. Due to the complexity of the original kinetic equation, only uniaxial extensional flow in a homogeneous monodomain is considered. The solution of the original kinetic equation without simplifications is obtained for the first time—using a finite difference scheme with an iterative procedure for an integral equation. The solution of the kinetic equation written in terms of the order-parameter tensor (a nonlinear algebraic equation) is obtained by Newton's procedure. For the ordered phase, the order-parameter version provides acceptable approximation only in the low-concentration region, the extent of which decreases with increasing velocity gradient. The hybrid approach of Edwards and Beris (1989) provides no improvement over the order-parameter version; in the presence of a strong flow, it actually gives worse results at low concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461573
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 54
    Electronic Resource
    Electronic Resource
    Determination of the translational order parameter in the liquid crystalline smectic A phase using the x-ray diffraction method (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6066-6074 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: On the basis of our recently suggested fan-shaped scattering model [J. Chem. Phys. 92, 5099 (1990)], a method to calculate the translational order parameter τ for the uniaxially oriented liquid crystalline smectic phase is suggested. Using this method, τ is determined from the scattering profiles of the two-dimensional inner reflexes for two samples of the liquid crystalline side chain polymer in their smectic A phase. The relationship between τ and the orientational order parameter 〈P2〉 is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461576
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 55
    Electronic Resource
    Electronic Resource
    Fractal and multifractal analysis of the sensitivity of catalytic reactions to catalyst structure (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6100-6111 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The effects of catalyst surface morphology and surface active-sites distribution on diffusion limited reactions are studied. The catalysts structures are deterministic and random Cantor sets (CS) and Devil's staircases (DS). The reaction is an Eley–Rideal process in which a random walker approaches the surface from the bulk and reacts with an active site upon collision with it. Two types of scaling analysis are performed: Fractal time scaling of product formation that provides a global analytical tool of the process; and multifractal analysis with which the complex distribution of reaction probabilities of the active sites are analyzed. Some of the main findings are (a) the fractal time scaling theory that has been applied successfully for connected fractal objects, also describes well the performance of disconnected, dust-type fractal objects such as found in most real catalysts and as modeled by the DS and CS; (b) the effective diffusion coefficient for reactions with disconnected active sets is smaller than for connected sets; we provide a method for calculating it; (c) despite the structural similarity of the DS and CS, they react with different efficiencies. It is shown that this difference can be explained in terms of kv, the prefactor of the neighboring-volume/yardstick-sized relation; (d) by performing the analyses on objects with various sizes, we provide evidence that corroborates the specific scaling assumptions of the multifractal formalism for the studied structures; and (e) significant differences between the τ(q) and f (α) multifractal spectra of the four objects are found and analyzed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461579
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 56
    Electronic Resource
    Electronic Resource
    Quantum scattering from disordered surfaces (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6136-6150 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A projected continuum formulation for time-independent quantum scattering from a continuum of channels is presented and applied to atomic scattering from disordered surfaces. Projecting out the channel continua gives rise to explicitly constructed optical potentials for the coherently diffracted scattering amplitudes, while the continuum diffuse scattering contribution is obtained in terms of these wave functions. Numerical application is made to atomic scattering from weakly corrugated disordered surfaces, for which a truncated set of coupled equations can be used within which the theory is shown to be unitary. The occurrence of a new phenomenon of disorder-induced sticking on rigid surfaces is demonstrated and comparison with phonon-induced sticking is made. These new disorder-induced sticking processes are shown to have very different energy dependence than phonon-induced sticking, with strong resonant sticking and oscillatory behavior seen at low incident energies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461582
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 57
    Electronic Resource
    Electronic Resource
    Collision-induced Coulomb explosion in mass-selected triply charged benzene clusters (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6175-6177 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461586
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 58
    Electronic Resource
    Electronic Resource
    Bound excited electronic states of anions studied by electron photodetachment spectroscopy (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6185-6187 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Excited electronic states of the radical anion of 7,7,8,8- tetracyanoquinodimethane (TCNQDN) which are stable with respect to electron loss have been observed by electron photodetachment spectroscopy. An onset for photodetachment is seen at 1.2 eV, considerably below the known binding energy (2.8 eV). We propose a sequential two-photon detachment process, supported by intensity dependence studies. TCNQDN is representative of a general class of anions which we believe will have such bound states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461589
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 59
    Electronic Resource
    Electronic Resource
    The role of matrix material and CCl4 (electron acceptor) on the ionization mechanisms of matrix-isolated naphthalene (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6190-6191 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The effects of matrix atoms (Ne vs Ar), photoionizing energy and CCl4 (electron acceptor) on the ionization mechanisms of naphthalene are discussed through their impact on the strength of the 300–900 nm spectrum of C10H+8. In Ne and Ar matrices containing naphthalene and CCl4, under 10.2 eV VUV irradiation, CCl+4 is predominantly formed (characterized by a broad, strong absorption at 408 nm in a neon matrix), severely limiting the naphthalene cation yield. As shown by Andrews et al. [J. Phys. Chem. 86, 2916 (1982)], with lower energy photon irradiation (5.6 eV), CCl4 is not ionized, but rather acts as a very efficient electron trap in argon, leading to a strong enhancement of the C10H+8 yield. However, naphthalene cations are not produced under the same conditions in a neon matrix. The difference between the ionization mechanism in the two matrices is explained in terms of spin–orbit coupling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461827
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 60
    Electronic Resource
    Electronic Resource
    Direct observations of pair interactions on a metal: Heteropairs on W(110) (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6075-6087 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Quantitative information about the range and strength of interactions between adatoms on surfaces is still scarce. However, through the use of the field ion microscope it is possible to pinpoint the location of individual metal atoms on a crystal, and therefore to establish by direct observation the probability P(R) of finding two atoms at sites separated from each other by the vector R. If equilibrium is established at the surface, this probability is related to F(R), the free energy of interaction, by P(R)∝exp[−F(R)/kT]; measurements of the probability therefore provide a quantitative estimate of the interaction between adatoms at specified sites on the surface. Such measurements have been carried out with two metal atoms on the most densely packed plane of tungsten, the (110). To minimize the amount of data taking, initial studies have been made on the distribution of an adatom (Pd) mobile at the temperature of equilibration around a chemically different metal atom (either Re or W) stationary at the center of the W(110) plane. These observations reveal a remarkable anisotropy. Palladium atoms are most frequently found at the nearest-neighbor position to the central atom, but the close by second and third-nearest neighbor sites are not populated. It is shown that this is due to a strong orientational dependence of interactions. Quantitative values for the free energy of interaction with the central adatom have been determined for Pd atoms at different sites on the surface. Along the close-packed direction [11¯1], interactions are attractive out to ≈10 A(ring), and show an oscillatory dependence upon distance; along [001] and [11¯0] they tend to be repulsive for both Re and W as the central atom. These effects are so far not predicted by theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461577
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 61
    Electronic Resource
    Electronic Resource
    Monte Carlo precise determination of the end-to-end distribution function of self-avoiding walks on the simple-cubic lattice (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6088-6099 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Chains have been generated on the simple-cubic lattice to determine, by Monte Carlo simulation, the end-to-end distribution function of self-avoiding walks. The modulus r of the end-to-end distribution vector r, the square of this modulus, and the interactions of all orders were recorded for each chain. The Alexandrowicz dimerization procedure has been used to circumvent attrition and thus obtain statistically significant samples of large chains. This made it possible to obtain samples involving 12 000–16 000 chains, within "windows'' of width Δρ=0.2, where ρ=r/Nν, N being the number of steps in the walk and ν the scaling exponent. It was found that the mean value 〈r〉=aNν, with ν=0.5919 and the prefactor a very close (perhaps strictly equal) to unity. The above value of ν is slightly larger than that calculated by Le Guillou and Zinn-Justin, but in accord with the Wilson ε=4−d expansion, where d is the space dimensionality. Also, 〈r 2〉=bN2ν, with b=1.136±0.05. An attempt was made to fit the data to the Fisher–McKenzie–des Cloizeaux distribution, P(r=Nνρ)=N−νdA ρθ exp(−βρδ), where θ, β, and δ are adjustable parameters. Taking δ=(1−ν)−1=2.45, in accordance with the Fisher law, it was found that plots for various N values of ln L(ρ)+βρδ vs ln ρ, where L(ρ) is the number of chains falling within subwindows of width dρ=0.02, were linear (except for the lowest values of ρ), if β was taken equal to 1.07. From the slope of the linear plot it was found that θ=0.27, in accord with theory. Finally, in three dimensions the end-to-end distribution function P(r) can be expressed by the relation P(r=Nνρ)=N−νd 0.2393ρ0.27 exp(−1.07ρ2.45). This relation is in good agreement with that proposed by des Cloizeaux and Jannink. A brief discussion of the two-dimensional case as well as fluctuations of the end-to-end distance is also presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461578
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 62
    Electronic Resource
    Electronic Resource
    Porous vycor glass: The microstructure as probed by electron microscopy, direct energy transfer, small-angle scattering, and molecular adsorption (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6151-6161 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We provide a comprehensive analysis of the microstructure of the porous glass, vycor. Using transmission electron microscopy, small-angle x-ray scattering, molecular adsorption, and the dynamic process of direct energy transfer, a consistent picture of the mass, pore, and interfacial features of this material is presented. From a transmission-electron-microscopy image of an ultrathin section of vycor the material appears to have a homogeneous distribution of mass with no hierarchical organization. The pore interface exhibits a roughness which is probed by both small-angle x-ray scattering and molecular adsorption. The roughness has an upper cutoff of 〈20 A(ring) which is not resolved in the transmission-electron-microscopy image and is shown to be unimportant to the dynamics of the direct energy transfer process. The dimensionality probed by direct energy transfer is shown to be related to interfacial geometrical crossover from two dimensional to three dimensional, which is characterized by a persistent length of the interface of 45 A(ring).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461583
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 63
    Electronic Resource
    Electronic Resource
    Competitive adsorption of two species: Doublet closure approximation and simulation (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6171-6174 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Starting from a master equation, competitive adsorption of two kinds of interacting particles on a linear chain is considered. The transition probabilities are chosen in the Arrhenius form, and the activation energy is split into two additive terms, corresponding, respectively, to the action of the substratum and to interactions between nearest neighbor adatoms. The kinetic equations are obtained by using a doublet closure approximation, writing triplet densities in terms of doublet and singlet densities. In this approximation, for the range of parameters being considered, only one stable steady state results, unlike in the case of the mean field approximation (where up to three stable steady states can exist). In view of the disagreement between the results of both approximations, a Monte Carlo simulation is carried out and results similar to those of doublet closure approximation are obtained. In neither of these two models interactions between nearest adatoms produce multistability. Thus, one may conclude that multistability resulting from the mean field model is spurious and caused by the approximations used. Therefore, the mean field approximation can be unsuitable for studying multistability in these kinds of problems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461585
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 64
    Electronic Resource
    Electronic Resource
    Electronic shell closings in metal cluster plus adsorbate systems: Cu+7CO and Cu+17CO (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6181-6184 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The stability of CO-chemisorbed small clusters of copper have been studied both by first principles calculations and by experiment. Evidence is found that the shell model (which predicts that clusters of 8, 18, and 20 electrons are particularly stable) is useful both for the bare metal clusters, and for these clusters with a chemisorbed CO−provided the CO is considered to have contributed two electrons. Experiments supporting this view are reported for gold clusters as well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461588
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 65
    Electronic Resource
    Electronic Resource
    Remarks on nonequilibrium contributions to the rate of chemical reaction in the Lorentz gas (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6192-6193 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The conception of nonequilibrium Shizgal–Karplus temperature is analyzed for a chemical reaction in three component Lorentz gas. The results for nonequilibrium contributions to the rate of chemical reaction obtained by this conception are similar to those obtained from perturbation method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461594
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 66
    Electronic Resource
    Electronic Resource
    Erratum: Thermodynamics of solid and liquid EAM metals: A variational study [J. Chem. Phys. 94, 5090 (1991)] (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6197-6197 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461842
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 67
    Electronic Resource
    Electronic Resource
    Electronic absorption spectra in a polar fluid: Theory and simulation (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 4756-4764 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present calculations of the inhomogeneously broadened absorption line shape associated with a single vibronic transition in a polar chromophore at infinite dilution in a polar solvent. The permanent electric dipole moment of the solute is assumed to change upon electronic excitation. The line shape is related to the dipolar solvation free energy of a fictitious solute with a complex-valued dipole moment. This relation allows methods of equilibrium fluid theory to be applied to the line shape calculation. In order to assess the accuracy of theoretical predictions, we determine line shapes from Monte Carlo simulations for a dipolar hard sphere solute in a dipolar hard sphere solvent. Simulated line shapes are compared to predictions of the mean spherical approximation (MSA) and to a simplified nonlinear solvation theory. The MSA is found to show semiquantitative agreement with simulation results, despite the large value of the solute's ground-state dipole moment and of its dipole moment change upon excitation. Simulation results are also compared to the relation between the first and second moments of the spectrum that is predicted by any linearized solvation theory. The comparison suggests that an "exact'' linearized theory would provide accurate predictions for absorption spectra in polar solutions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461718
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 68
    Electronic Resource
    Electronic Resource
    Solid state proton spin relaxation and t-butyl and methyl group reorientation in 1-bromo-2,4,6-tri-t-butylbenzene (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 4778-4782 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have used the solid state proton spin relaxation technique to investigate the barriers for methyl and t-butyl group reorientation in polycrystalline 1-bromo-2,4,6-tri-t-butylbenzene. The barriers in the range of 15–19 kJ/mol (3–5 kcal/mol) are compared with those found in related molecules. It is shown that the neighboring ring bromine atom has an effect on the barrier for t-butyl group reorientation similar to that of a neighboring hydrogen atom despite the significantly larger van der Waals' radius of a bromine atom. This most likely occurs because of the relatively long carbon–bromine bond, the distorted ring geometry, and the relatively high polarizability of bromine. In addition, the barriers for methyl group reorientation, about 16 kJ/mol, seem to be largely intra-t-butyl in origin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461720
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 69
    Electronic Resource
    Electronic Resource
    Quadrupole echoes and the 127I nuclear hexadecapole interaction in KI (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 4796-4801 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A quadrupole echo method for searching for the nuclear hexadecapole interaction (HDI) is described. A sequence of three radio frequency pulses applied at times 0, τ, and nτ (n〉1) gives a simple pattern of nuclear spin (5)/(2) echoes when only the nuclear Zeeman and quadrupole interactions are present. Calculations for n=2.5, 3.0, 4.0, and 5.0 show that these patterns undergo an elaborate change when the HDI is also present and that these echo patterns are unique to the HDI. Three pulse echoes were used to search for the 127I HDI in a single crystal of KI but, for this sample, a two pulse sequence was found to be more effective. For KI, 2.8 kHz is the estimated magnitude of the 127I hexadecapole coupling constant, eHV(4)/h, where eH is the 127I electric hexadecapole moment and V(4) is a fourth derivative of the electrostatic potential at the nuclear site. This is the smallest HDI measured in a solid so far.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461723
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 70
    Electronic Resource
    Electronic Resource
    Zero kinetic energy electron spectroscopy of molecules: Rotational symmetry selection rules and intensities (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 4821-4839 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The rotationally resolved "zero kinetic energy (ZEKE)'' photoelectron spectra for linear and planar molecules are interpreted as transitions into highly excited Rydberg states corresponding to Hund's coupling case (d). The general case (d) is described for planar and linear molecules. The observed ZEKE transitions can be understood in terms of near-symmetry selection rules for the one-electron states involved. The proposed model consists of two steps: photon absorption leads to a state where the angular momentum of the excited electron is still coupled to the figure axis (the internuclear axis for diatomics and the highest symmetry axis for planar molecules). For planar molecules this leads to a selection rule for the projection quantum number K. The second step is the decoupling of the excited electron from the figure axis and its recoupling to the total angular momentum vector of the ion core. The decoupling process is assumed to occur adiabatically and hence with preservation of the electronic symmetry of the excited electron state. This leads to a selection rule for the total angular momentum N and explains the occurrence of only a single peak with v+2=1, N+=4, K+=3 in the ZEKE spectrum of the B˜ state of ortho-NH3 with v2=2, JB=3, KB=1. Also, analytical formulas are presented for the intensities of 1+1 and 2+1 photoionization processes including the alignment of the intermediate state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461700
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 71
    Electronic Resource
    Electronic Resource
    The wave packet motion and intramolecular vibrational redistribution in CHX3 molecules under infrared multiphoton excitation (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 4854-4876 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report results from quantum dynamical simulations of ultrafast vibrational redistribution processes in the CH chromophore of CHX3 molecules (CHD3, CHF3) during and after infrared-multiphoton excitation. The vibrational Hamiltonian is based on results from high resolution spectroscopy and ab initio calculations of the potential hypersurfaces for these molecules. The quantum dynamical calculations involve accurate solutions of the time dependent quantum equations of motion by means of both Floquet and quasiresonant approximations. We find mode selective redistribution between the CH stretching and bending modes on a time scale of 50 to 100 fs. Other modes participate only on much longer time scales (〉1 ps), as was shown previously by analysis of the spectra. For the real, strongly anharmonic systems (k'sbb(approximately-equal-to)30 to 100 cm−1 ), the redistribution is nonclassical with fast spreading to a quasimicrocanonical distribution, which is particularly pronounced if a narrow range of energies (for example, the N=6 polyad) is initially excited. The effect can be interpreted as an intrinsic quantum statistical behavior induced by anharmonicity. In comparison, a weakly anharmonic hypothetical model system (ksbb≤2 cm−1) leads to quasiclassical motion of the wave packet with quasiperiodic exchange between stretching and bending motions. We present an approximate analytical investigation of the Fermi modes underlying the dynamics which provides a semiquantitative understanding of the Fermi-resonance spectra. On the basis of these results, we discuss possibilities of mode selective reaction control in unimolecular processes with laser excitation and some aspects of intramolecular "chaos.''
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461703
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 72
    Electronic Resource
    Electronic Resource
    Model calculations for halogen-etching of GaAs and InSb. Potential-energy surfaces for GaAs+Cl, GaAs+Br, InSb+Cl, and InSb+Br reactions (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 4905-4913 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have investigated the potential-energy surfaces of GaAs+Cl, GaAs+Br, InSb+Cl, and InSb+Br reactions as a function of electronic state and orientation. We employed a complete active space multiconfiguration self-consistent field followed by multireference configuration interaction calculations to study the potential-energy surfaces of these species. We find that the collinear mode of approach in which the halogen atom approaches the group-III atom (Ga, In) is the most favorable approach. The loosely bound Cl–Ga...As (Br–Ga...As) complex is shown to be formed which would undergo ready desorption to emit mostly GaCl (GaBr). Our computed potential-energy surfaces explain the observed laser-induced desorption products in halogen-etching of a GaAs surface as well as HCl-etching of GaxAs−y. We also computed the spectroscopic constants of GaX, InX, AsX, and SbX (X=Cl, Br).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461706
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 73
    Electronic Resource
    Electronic Resource
    Singlet molecular oxygen excitation of BrF B 3Π(0+) (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 4933-4939 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The excitation of BrF B 3Π(0+) by metastable singlet oxygen, O2(a 1Δ,b 1Σ), has been studied under steady-state conditions in a flow tube reactor. The chemiluminescence from BrF(B) indicates a nonthermal vibrational distribution that peaks at v'=3 and a ratio of BrF(B) to O2(b 1Σ+g) concentration of about 5×10−4. The emission is attributed to three-body recombination of bromine and fluorine atoms with a rate coefficient of approximately 7×10−31 cm6/molecule2 s and a single-step energy-transfer collision with O2(b 1Σ). The rate coefficients for quenching of O2(b 1Σ) by CO2, CF4, Br2, and Br have been determined from a linear Stern–Volmer analysis as 3.0, 0.027, 9.7, and 140×10−13 cm3/molecule s, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461709
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 74
    Electronic Resource
    Electronic Resource
    Inelastic processes in e–HCl collisions in the energy range including the dissociation threshold (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 4966-4971 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Inelastic processes in low-energy collisions of electrons with HCl molecules are considered. We present results of calculations of vibrational excitation cross sections from the ground state and vibrationally excited states, dissociative attachment cross sections, and electron-impact dissociation cross sections near threshold. Our approach is based on the resonance R-matrix theory with the quasiclassical treatment of the nuclear motion. We use a rigorous procedure for the inclusion of the vibrational continuum. This allows for calculations of the cross sections in the energy range including dissociation threshold. The results for the dissociation cross sections are analyzed from the point of view of the threshold law for the three-particle break-up process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461713
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 75
    Electronic Resource
    Electronic Resource
    Quantum mechanical study of the reaction He+H+2→HeH++H with hyperspherical coordinates (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5159-5168 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Integral cross sections for the reaction He+H+2→HeH++H have been computed with the hyperspherical method in the threshold energy range. The ab initio potential of McLaughlin and Thompson, fitted by Joseph and Sathyamurthy, has been used. A lifetime matrix analysis of the J=0 reaction probabilities shows the existence of many long-lived resonances, with several having lifetimes as long as 3.1 ps. The magnitude of the total reaction cross section is in reasonably good agreement with the experimental result of Chupka (1968).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461684
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 76
    Electronic Resource
    Electronic Resource
    General formula evaluation of the electron-repulsion integrals and the first and second integral derivatives over Gaussian-type orbitals (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5198-5205 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Recurrence relations between auxiliary functions to calculate the electron-repulsion integrals (ERIs) over Cartesian Gaussian-type orbitals (GTOs) can be derived. With the use of the Rys polynomials, this serves as a general formula method for evaluating ERIs and the ERI analytical derivatives. The computer code of the present method is quite general (i.e., it has no limitation for the shell type of GTOs), very compact (i.e., it has no coding difficulty), and extremely rapid (e.g., 2.1 μs per one ERI, 0.51 μs per one ERI first derivative, and 0.40 μs per one ERI second derivative for the [II||II] shell block). It is found that the present method is especially efficient for evaluating ERIs including g-type or higher GTOs, the first derivatives including f-type or higher GTOs, and the second derivatives including d-type or higher GTOs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461688
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 77
    Electronic Resource
    Electronic Resource
    On the theory of electrostatic interaction of neutral lipid bilayers separated by thin water film (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5224-5229 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A simple analytical solution is obtained for the screened Coulombic force between neutral lipid bilayers separated by thin water film within a model formally analogous to the "spherical model'' for Ising systems. This model accounts for constraints on the surface charge density fluctuations imposed by the structure of lipid bilayers. The force is attractive at low and repulsive at high temperatures. A relationship between the system parameters and the temperature of the transition from the repulsion to attraction is established. At room temperature predicted force can be repulsive as well as attractive depending on the system parameters and on the assumptions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461693
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 78
    Electronic Resource
    Electronic Resource
    Thermophysical properties of gaseous refrigerants from speed-of-sound measurements. III. Results for 1,1-dichloro-2,2,2-trifluoroethane (CHCl2-CF3) and 1,2-dichloro-1,2,2-trifluoroethane (CHClF-CClF2) (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5236-5242 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The speed of sound in gaseous 1,1-dichloro-2,2,2-trifluoroethane (CHCl2CF3, commonly known as R123) has been measured at temperatures T between 260 and 335 K at pressures p from 1.6 to 77 kPa. Perfect-gas heat capacities and second and third acoustic virial coefficients have been calculated from the results. The second and third acoustic virial coefficients are used to estimate the density virial coefficients B(T ) and C(T ) and an effective square-well potential. The acoustic estimates of B(T ) and C(T ) are consistent with B(T ) and C(T ) deduced from high-quality (p,Vm, T ) results. The combined values of B(T ) and C(T ) cover a reduced temperature range of 0.57 to 0.99. We have also measured the speed of sound in 1,2-dichloro-1,2,2-trifluoroethane (CHClF-CClF2, commonly known as R123a). This isomer of R123 is a significant impurity in R123 as manufactured and used. We provided estimates of the vibrational relaxation time for R123.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461831
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 79
    Electronic Resource
    Electronic Resource
    Molecular dynamics of a model SN1 reaction in water (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5256-5267 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Results are presented from a computer simulation of the dynamics of a model SN1 reaction in water, very loosely based on the reaction t-BuCl→t-Bu++Cl−. Two diabatic electronic states are considered, covalent and ionic, which cross in the presence of the polar solvent. The curve crossing is treated in the electronically adiabatic limit, which gives rise to coupled reagent and solvent dynamics involving a mixed covalent/ionic adiabatic potential surface. The reaction dynamics are analyzed in terms of a simple solute reaction coordinate defined to be the t-Bu to Cl separation distance. By employing constraint dynamics techniques, the potential of mean force is determined as a function of this reaction coordinate. The time evolution of the reaction is followed in terms of the full molecular dynamics of all reagent and solvent atoms. Beginning with the largely covalently bound reactant t-BuCl, the following was observed: (i) how energy flows out of the water solvent bath into a solvent–reactant fluctuation driving the system to the top of the barrier, (ii) how barrier recrossings lower the reaction rate below the transition state theory prediction, and (iii) how the products slide down the barrier toward separated t-Bu+ and Cl−, dissipating their excess energy back into the solvent. The calculated transmission coefficient measuring the departure of the rate constant from its transition state theory value is 0.53±0.04. This is found to agree with the Grote–Hynes theory prediction, and also with its nonadiabatic solvation, frozen solvent limit, to within the estimated error bars. By contrast, Kramers' theory incorrectly predicts a much smaller value.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461697
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 80
    Electronic Resource
    Electronic Resource
    The application of integral equation theories to fluids of nonspherical particles near a uniform planar wall (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5281-5288 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A general reduction of the Ornstein–Zernike equation is given for molecular fluids near a planar wall. This allows integral equation approximations such as the hypernetted-chain or reference hypernetted-chain (RHNC) theories to be solved numerically for such systems. Dipolar hard sphere fluids near a hard wall are considered in detail and RHNC solutions are obtained. The results are compared with previous calculations for curved surfaces. The RHNC result for the asymptotic behavior of the wall–solvent pair correlation function at large separations is derived and compared with expressions given by classical continuum theory and by exact analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461667
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 81
    Electronic Resource
    Electronic Resource
    Molecular hydrodynamic theory of non-Markovian collective orientational relaxation in dense dipolar liquids (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5289-5299 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A microscopic study of the non-Markovian (or memory) effects on the collective orientational relaxation in a dense dipolar liquid is carried out by using an extended hydrodynamic approach which provides a reliable description of the dynamical processes occuring at the molecular length scales. Detailed calculations of the wave-vector dependent orientational correlation functions are presented. The memory effects are found to play an important role; the non-Markovian results differ considerably from that of the Markovian theory. In particular, a slow long-time decay of the longitudinal orientational correlation function is observed for dense liquids which becomes weaker in the presence of a sizeable translational contribution to the collective orientational relaxation. This slow decay can be attributed to the intermolecular correlations at the molecular length scales. The longitudinal component of the orientational correlation function becomes oscillatory in the underdamped limit of momenta relaxations and the frequency dependence of the friction reduce the frictional resistance on the collective excitations (commonly known as dipolarons) to make them long lived. The theory predicts that these dipolarons can, therefore, be important in chemical relaxation processes, in contradiction to the claims of some earlier theoretical studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461830
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 82
    Electronic Resource
    Electronic Resource
    Charge fluctuation in reverse micelles (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5318-5326 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Electrostatic interactions in and among reverse micelles in the microemulsion are studied by the grand canonical ensemble Monte Carlo simulation (GCEMC) and by the linear response/Poisson–Boltzmann approximation (LPB). The latter theory is found to reproduce the ion-correlation effects among the micelles seen in the earlier canonical Monte Carlo approach. The open ensemble simulation and the Poisson–Boltzmann (PB) equation are used to study solubilization of simple electrolyte in the microemulsion. In systems with monovalent ions, the PB approximation agrees well with the simulation. Since individual ions are allowed to enter or leave the micelle in our GCEMC simulation, the deviations from the electroneutrality of the droplets are also studied. A good agreement with the LPB theory and with the simple charge fluctuation models considering only the Born solvation energy of charged droplets is observed. For large reverse micelles, the LPB theory and the continuum approach of Eicke and co-workers [J. Phys. Chem. 93, 314 (1989)] proved satisfactory while only the discrete model of Hall [J. Phys. Chem. 94, 429 (1990)] agrees with the simulation for small droplets. The GCEMC results lend support to recent interpretations of electric conductivity of microemulsions. The intermicellar forces due to the correlated charge fluctuation on adjacent droplets are discussed. An approximate expression for the charge fluctuation contribution to the long-ranged pair potential among large droplets with the radius Rm of the form w(r)/kT(approximately-equal-to)−(1/2)(Rm/r)2 is derived.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461671
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 83
    Electronic Resource
    Electronic Resource
    Segmental distribution functions for a micelle comprised of small symmetric diblock copolymers (short chain amphiphiles) (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5341-5347 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The micelle formed by short chain amphiphiles (small diblock copolymers) in a selective solvent has been simulated on a cubic lattice. The system contains twenty chains, each with ten beads of A and ten beads of B, at a volume fraction of 0.0376. These chains form a single micelle when the pairwise interaction of nonbonded beads in the insoluble block contribute an energy of −0.5 kT, all other interaction energies being zero. The micelle consists of an internal core that is a close packed region occupied almost exclusively by the insoluble blocks, and a corona, the outer portion of which consists primarily of solvent and the soluble blocks. However, the interface between these two regions is not sharp, as judged by distribution functions for the two types of beads, and for the junctions between the blocks. Letting 〈r 2j〉 denote the mean square radius of gyration of the junctions, the close packed core of insoluble beads extends from the center of mass no farther than ∼0.5 〈r 2j〉. The free ends of the insoluble block have a mean square radius of gyration of 0.88 〈r 2j〉, which places them, on average, farther from the center of mass than a randomly chosen bead in the insoluble block. The results are not compatible with models for a diblock copolymer micelle that assume a sharp interface, nor with models that assume the free ends of the insoluble block seek out the center of mass, or are randomly distributed throughout the core.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461648
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 84
    Electronic Resource
    Electronic Resource
    Reduced partial cross sections for UV photodesorption of molecules from finite temperature surfaces (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5364-5372 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A wave packet dynamical formalism was recently introduced [J. Chem. Phys. 92, 5712 (1990)] for extracting photofragmentation distributions of specified "primary'' internal modes while summing implicitly over transitions to all other "secondary'' internal degrees of freedom. This reduced partial cross section formalism is useful for analyzing photodesorption of a molecule from a solid surface, since it enables direct computation of internal state distributions of the desorbed molecule without having to explicitly resolve all vibrational transitions of the lattice oscillators. The original formulation of the method considered only zero temperature systems. In the present paper the formalism is extended to treat systems prepared at finite temperatures. Two applications, focusing on vibrational and rotational excitation of diatomic desorbates, respectively, are presented in order to illustrate the versatility of the methodology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461651
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 85
    Electronic Resource
    Electronic Resource
    Calculated properties of solid N2O at various temperatures and pressures (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5399-5402 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Properties of solid N2O at pressures P≤15 GPa and at temperatures T=0 and 300 K have been calculated using energy optimization, Monte Carlo methods in an (N,P,T) ensemble with periodic, deformable boundary conditions, and lattice dynamics. A stable Pa3 structure is predicted at zero pressure and a phase transition into an orthorhombic Cmca phase is predicted at P=4.75 GPa, with a volume change ΔV(approximately-equal-to)0.25 cm3/mole. These results are in complete agreement with experiments conducted in conjunction with this work. Calculated libron frequencies are in agreement with recent Raman measurements. In addition, second virial coefficients, lattice parameters, internal energies, and pressure-volume relations have been calculated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461656
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 86
    Electronic Resource
    Electronic Resource
    Subpicosecond transient infrared spectroscopy of adsorbates. Vibrational dynamics of CO/Pt(111) (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5403-5418 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The vibrational dynamics of excited CO layers on Pt(111) were studied using infrared (IR) pump–probe methods. Resonant IR pulses of 0.7 ps duration strongly pumped the absorption line (ν≈2106 cm−1 ) of top-site CO. Weak probe pulses delayed a time tD after the pump were reflected from the CO-covered Pt(111) surface, and dispersed in a monochromator to determine the absorption spectrum of the vibrationally excited CO band, with time resolution 〈1 ps and monochromator resolution 〈1 cm−1. Transient spectra were obtained as a function of CO coverage, surface temperature, and laser fluence. Complex spectra for tD〈0 show features characteristic of a perturbed free induction decay, which are expected based on multiple-level density-matrix models. For tD≥0, the CO/Pt absorption exhibits a shift to lower frequency and an asymmetric broadening which are strongly dependent on fluence (1.3–15 mJ/cm2 ). Spectra return to equilibrium (unexcited) values within a few picoseconds. These transient spectral shifts and the time scale for relaxation do not depend (within experimental error) on coverage for 0.1≤aitch-thetaCO≤0.5 ML or on temperature for 150≤Ts≤300 K. A model for coupled anharmonic oscillators qualitatively explains the tD〉0 spectra in terms of a population-dependent decrease in frequency of the one-phonon band, as opposed to a transition involving a true CO(v=2) two-phonon bound state. The rapid relaxation time and its insensitivity to Ts and aitch-thetaCO are consistent with electron–hole pair generation as the dominant decay mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461657
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 87
    Electronic Resource
    Electronic Resource
    Adsorbate-assisted adsorption: Trapping dynamics of Xe on Pt(111) at nonzero coverages (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5437-5443 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The trapping dynamics of Xe on Pt(111) has been probed as a function of Xe coverage with supersonic molecular-beam techniques. Adsorption probabilities were directly measured at a surface temperature of 95 K at coverages ranging from zero to monolayer saturation at incident translational energies between 6 and 63 kJ/mol and incident angles between 0° and 60°. In apparent agreement with the predictions of the original Kisliuk model, the adsorption probability at the lowest incident translational energy (6 kJ/mol) remains almost constant with coverage up to near monolayer saturation. However, in contradiction to the original Kisliuk model, at higher incident translational energies, the trapping probability increases nearly linearly with xenon coverage up to near monolayer coverage. For example, the trapping probability increases from 0.06 to 0.42 for an incident translational energy of 63 kJ/mol at normal incidence as the coverage is increased from zero to saturation monolayer coverage. This behavior can be explained adequately by a model that incorporates enhanced trapping onto the monolayer compared to the clean surface, a property of the model that is confirmed directly by experiments presented herein. The angular dependence of the adsorption probability shows progressive deviation from normal energy scaling with increasing Xe surface coverage, proving that the degree to which parallel momentum participates in the adsorption process increases with adsorbate coverage. The initial trapping probability of Xe onto the monolayer is independent of incident angle indicating total-energy scaling. The above findings are qualitatively identical to our previous results for the molecular adsorption of ethane on the same surface, suggesting that these phenomena occur, in general, for weak molecular adsorption regardless of molecular shape and internal degrees of freedom, at least for small molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461660
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 88
    Electronic Resource
    Electronic Resource
    Rotationally resolved V–V transfer in C2D2/Ar collisions: Characterization of a vibrational bottleneck (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5476-5478 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Time-resolved infrared–ultraviolet (IR–UV) double resonance spectroscopy is employed for rotationally resolved kinetic studies of collision-induced energy transfer between the 4151 and 42 vibrational levels in the ground electronic state of acetylene-d2, C2D2. Second-order rate constants, for intra- and intermolecular V–V transfer and also for V–T,R transfer, are determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461663
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 89
    Electronic Resource
    Electronic Resource
    State-selective physisorption of deuterated ammonia on graphite (0001) (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5486-5488 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rotationally state-selected molecular beams of ND3 at 0.11 eV are directed at near-normal incidence to a graphite (0001) surface. The relative number density in the scattered beams, measured by photoionization spectroscopy, is found to be two times greater for the incident molecular beam of predominantly ||JKM〉=||222〉 rotational states as compared to the ||111〉 beam, implying state-selective trapping.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461644
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 90
    Electronic Resource
    Electronic Resource
    Erratum: Trapping of finite-sized Brownian particles in porous media [J. Chem. Phys. 95, 2838 (1991)] (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5492-5492 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461841
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 91
    Electronic Resource
    Electronic Resource
    Pressure broadening data as a test of a recently proposed Ar–H2O interaction potential (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 3888-3890 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An interaction potential for H2O–Ar that was recently determined from spectra of the van der Waals complex [R. C. Cohen and R. J. Saykally, J. Chem. Phys. 94, 7991 (1990)] is used with accurate molecular scattering calculations to predict line broadening parameters for the 183 and 380 GHz transitions of water vapor. Theoretical values are about 15% higher than experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460795
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 92
    Electronic Resource
    Electronic Resource
    The onset of intramolecular vibrational energy redistribution and its intermediate case: The ν1 and 2ν1 molecular beam, optothermal spectra of trifluoropropyne (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 3891-3916 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Using the optothermal method for molecular beam, infrared spectroscopy, we have measured both the fundamental and first overtone of the acetylenic C–H stretch in CF3CCH. In the fundamental we observe a spectrum which shows only few perturbations. The majority of lines can be successfully fit to a model assuming an anharmonic coupling of the C–H stretch to a single, near-resonant background state with a coupling matrix element of 0.006 cm−1. We have observed other perturbations in this spectrum, including a state coupled by a weak perpendicular Coriolis interaction. All observed couplings are very weak and local in nature. In the overtone, where the density of background states increases by a factor of 100, we observe a spectrum characteristic of a system in the intermediate case of IVR (intramolecular vibrational energy redistribution). Analysis of the R(0) and P(1) transitions provides a homogeneous IVR lifetime of about 2 ns, which is long compared to lifetimes generally quoted for overtone vibrational relaxation. The root-mean-square coupling matrix element in the overtone is about 0.0008 cm−1. The higher J transitions in the overtone suggest that Coriolis interactions are present in the spectrum. The interpretation of these spectroscopic results in the context of IVR is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460796
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 93
    Electronic Resource
    Electronic Resource
    The C 3Π–X 3Π band system of the SiC radical (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 3939-3943 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report a study of the C 3Π–X 3Π band system of the SiC radical. Jet-cooled SiC is produced by a laser vaporization/pulsed beam source and is probed by pulsed laser-induced fluorescence excitation spectroscopy. Vibrational term energies and rotational constants are determined for v'=0–8 of the C state and for v‘=0–5 of the X state. The spectroscopic constants for the C state are Te=22 830.4(9) cm−1, ωe=615.7(8) cm−1, and re=1.919(3) A(ring); for the X state, ωe=965.16(24) cm−1 and re=1.7182(2) A(ring).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460800
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 94
    Electronic Resource
    Electronic Resource
    Fourier transform infrared spectroscopy of the ν3 band of cyclopropenylidene, C3H2 (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 3975-3979 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The gas-phase absorption spectrum of the ν3 band of cyclopropenylidene (cyclic C3H2 ) has been observed with a high-resolution Fourier transform infrared spectrometer. The ring molecule was generated by a microwave discharge in an allene and Ar mixture. The spectrum observed between 1250 and 1305 cm−1 was analyzed by using Watson's A-reduced Hamiltonian to determine the band origin (ν0=1277.3711±0.0001 cm−1 ), rotational constants, and centrifugal distortion constants in the ν3 state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460804
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 95
    Electronic Resource
    Electronic Resource
    Photodissociation spectroscopy of benzene cluster ions: (C6H6)+2 and (C6H6)+3 (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 4002-4009 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photodissociation of size-selected benzene cluster ions, (C6H6)+m+hω→(C6H6)+n+ (m−n)C6H6, has been investigated in the 410–750 nm wavelength range using tunable dye laser radiation. The measurements were performed using a tandem mass spectrometer [a linear time-of-flight (TOF)/reflectron TOF] combined with multiphoton ionization (MPI) for ion preparation. Only C6H+6 was detected as a photofragment of (C6H6)+2 and (C6H6)+3, while both C6H+6 and (C6H6)+2 fragments were observed in the case of (C6H6)+4 photodissociation. Photodissociation spectra, i.e., photofragment yield spectra as a function of wavelength, of (C6H6)+m (m=2,3) were obtained. Two local excitation bands of (C6H6)+m were seen in this region and assigned to the C(A2u)←X(E1g) and the B(E2g)←X(E1g) transitions of a C6H+6 unit in the clusters. The origin of the B←X transition of (C6H6)+2 and (C6H6)+3 was redshifted relative to that of C6H+6 by about 1400 and 2400 cm−1, respectively, while the C←X bands of (C6H6)+2 and (C6H6)+3 were seen at the same wavelengths of 440 nm. Possible structures for the cluster ions are discussed based on the spectral shifts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460807
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 96
    Electronic Resource
    Electronic Resource
    Electron spin resonance study on the structure and dynamics of propane cation radical: The intrinsic form with a CS symmetry (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 3955-3963 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Propane cation radicals with CS symmetry were found by electron spin resonance in C3F8 and C2F6 at 4 K. They have one C–C bond elongated considerably, and the unpaired electron is in the 10a' orbital of CS symmetry, which is derived from the 4b1 orbital of C2V symmetry by the deformation. The highest spin density appears in the elongated C–C bond, and the in-plane methyl proton at the other end has the largest hyperfine coupling (hfc) of about 9 mT. The degree of deformation from the C2V form is dependent on the matrices. From the general consideration on the structure of propane cation, it is deduced that the cation in SF6, which has been considered to have C2V symmetry, also has CS symmetry with a smaller distortion, and that distortion to CS symmetry is an intrinsic nature of the propane cation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460802
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 97
    Electronic Resource
    Electronic Resource
    Fundamental stretching frequencies in 1H13C14N– –1H19F: J-dependent predissociative excited state lifetimes in ν3 (C≡N) stretching vibration (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 3980-3990 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Static gas phase rovibrational analyses have been used to determine the four fundamental stretching band origin frequencies (in cm−1) of 1H13C14N– – –1H19F: ν1=3716.100(3), ν2=3292.1029(3), ν3=2088.9209(7), ν4=167.407(5). Estimated lifetimes in the ν1 and ν3 vibrationally predissociating states are determined to be τ(ν1)=0.052(7) ns; and τ(ν3)=1.1(3) ns, J'≤16; τ(ν3)=0.32(5) ns, J'≥17. The availability of a higher HF rotational energy channel is proposed as a possible mechanism for explaining this sudden change in excited state lifetime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460805
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 98
    Electronic Resource
    Electronic Resource
    Influence of two-photon absorption on third-order nonlinear optical processes as studied by degenerate four-wave mixing: The study of soluble didecyloxy substituted polyphenyls (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 3991-4001 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have investigated the influence of two-photon absorption on the third-order nonlinear optical properties of model organic molecules using the technique of degenerate four-wave mixing (DFWM). A theoretical formulation developed here shows that the presence of two-photon absorption, which is related to the imaginary part of the third-order susceptibility χ(3), leads to an enhancement of the effective third-order nonlinearity and to the appearance of effects caused by the formation of two-photon generated excited states. The dynamic behavior of the nonlinearity is then governed by the properties of excited molecules. The nonlinear effects also involve contributions which depend on the fifth power of the electric field. We have performed a systematic study of third-order nonlinear optical properties of alkoxy (–C10H21OCH) substituted p-polyphenyl oligomers using the technique of time-resolved degenerate four-wave mixing with subpicosecond pulses at 602 nm. Experimentally determined values of the second-order hyperpolarizability γ for the oligomers increase smoothly from the monomer to the trimer, with a more rapid increase to the pentamer and to the heptamer. In addition, the hyperpolarizabilities for the pentamer and the heptamer appear to be complex. A smooth increase of the γ value is expected from an increase of the π conjugation from a shorter chain oligomer to a longer chain oligomer. The more rapid increase of the γ value in the pentamer, and especially in the heptamer, however, cannot be explained satisfactorily by only taking into account the π-conjugation length. Two-photon absorption for the pentamer and the heptamer at the measurement wavelength of 602 nm is suggested to be important as the observed dynamic behavior is satisfactorily explained by the predictions of the theoretical model presented here. It is shown that the effective γ value for a two-photon absorbing material is a function of optical intensity, pulse width, and sample length if one uses the conventional degenerate four-wave mixing description.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460806
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 99
    Electronic Resource
    Electronic Resource
    Energies of CH2OH, CH3O, and related compounds (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 4040-4043 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Gaussian-2 (G2) theoretical procedure, based on ab initio molecular orbital theory, is used to calculate the energies of CH2OH, CH3O, and their cations. The resulting G2 adiabatic ionization potential for CH3O of 10.78 eV supports the new value of 10.726±0.008 eV reported by Ruscic and Berkowitz [J. Chem. Phys. 95, xxxx (1991)] from a photoionization study. A previous photoelectron result of 7.37±0.03 eV is probably an incorrect assignment. The G2 ionization potential for CH2OH is 7.45 eV, consistent with the experimental value of 7.55 eV. The calculated O–H and C–H bond dissociation energies of CH3OH are 105.0 and 96.2 kcal/mol, respectively. The results suggest that the D0(H–CH2OH) from kinetics measurements may be too low.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460759
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 100
    Electronic Resource
    Electronic Resource
    Differential cross section as a function of the product internal state: The F+I2→IF(v,J)+I reactive collision (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 4056-4069 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have measured the differential cross section of the F+I2→IF+I reactive collision as a function of the rovibrational state of IF. This measurement was made by an analysis of the Doppler profiles of the laser-induced fluorescence detection signals, as suggested by Kinsey [J. Chem. Phys. 66, 2560 (1977)]. This paper describes in detail the experiment and the way we analyze the data to deduce the differential cross section. The shape of the cross section appears to vary noticeably with the rotational energy of IF and to a lesser extent with its vibrational energy. Several partial explanations are possible, and the choice remains not clear as long as we have no precise information on the potential-energy surfaces of the I2F system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460761
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...