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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 6644-6659 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We compute energy levels and wave functions of Ne, Ar, Kr, and Xe trimers, modeled by pairwise Lennard-Jones potentials, using the discrete variable representation (DVR) and the successive diagonalization-truncation method. For the Ne and Ar trimers, we find that almost all of the energy levels lie above the energy required classically to achieve a collinear configuration. For the Kr and Xe trimers, we are able to determine a number of energy levels both below the classical transition energy as well as above it. Energy level statistics for these heavier clusters reveal behavior that correlates well with classical chaotic behavior that has previously been observed above the transition energy. The eigenfunctions of these clusters show a wide variety of behavior ranging from very regular behavior for low lying eigenstates to a combination of regular and irregular behavior at energies above the transition energy. These results, along with quantum Monte Carlo calculations of the ground states for a variety of small clusters, lead to the construction of a local mode model for the eigenstates of these clusters. This simple model reproduces quite well many of the calculated energy levels. From the findings here, a simple picture emerges for quantum mechanical clusters of Ne, Ar, Kr, and Xe that correlates very strongly to classical models of these systems.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 8254-8259 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The thickness of the interface between two-dimensional fluid phases is determined as a function of temperature by using the method of molecular dynamics. The model fluid is one of particles interacting via a truncated Lennard-Jones potential. Periodic boundary conditions are used and no macroscopic external field such as gravity is imposed. The temperature is varied between that of the triple point to values as close to the critical point as is consistent with the finiteness of the system studied on the computer. Because of the relatively small interfacial area probed in these simulations, long-wavelength capillary waves are strongly suppressed and within statistical uncertainty, the results for the interfacial thickness are found to be consistent with the prediction of the nonclassical van der Waals theory of the intrinsic interface.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 3470-3476 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The successive diagonalization–truncation method is applied to the calculation of the vibrational eigenvalues of the Ar trimer bound by pairwise Lennard-Jones potentials. The statistics of the eigenvalues reveal strongly chaotic behavior of the cluster, consistent with the classical dynamics studies. Moreover, the zero-point energy is higher than the highest energy at which regular dynamics were found classically, indicating that for all energies physically accessible to the cluster, the dynamics are chaotic.
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 1774-1786 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The successive truncation–diagonalization method described in previous work [Z. Bacic, R. M. Whitnell, D. Brown and J. C. Light, Comp. Phys. Comm. (to be published)] is generalized to a three-dimensional discrete variable representation (DVR). The use of the 3D DVR leads to a sparse Hamiltonian matrix that makes the transformations used in the successive truncation-diagonalization technique very efficient. The method is applied to J=0 H+3 using a hyperspherical coordinate system. Full symmetry adaptation of the DVR is used allowing a complete resolution of the vibrational eigenfunctions into the D3h irreducible representations. Converged eigenvalues up to ∼20 000 cm−1 are reported for all representations. This method is thereby shown to be both efficient and accurate for calculating triatomic vibrational states with large amplitude motion.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 2925-2931 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Resonance enhanced multiphoton ionization (REMPI) has been used to study the products of the infrared multiphoton decomposition (IRMPD) of CF3I in a very low-pressure photolysis (VLPΦ) cell. The strongest REMPI signals are due to the ground state I(2P3/2) and the spin–orbit excited state I*(2P1/2). The origins of I and I* were determined from the time and IR laser fluence dependences of the REMPI signal. I* is formed by visible single photon dissociation of vibrationally excited CF3I and by visible multiphoton dissociation of I2 and thermal CF3I. The ionization efficiency of I has been determined relative to NH3 for our probe laser conditions, and the sticking coefficient of I with gold surfaces has been determined. The REMPI spectra of the products of the IRMPD of CF3Br is also presented.
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 762-769 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In our efforts to examine the validity of the Kramers' equation, the rate constants of the excited state isomerization of 1,1'-binaphthyl in n-alkane solvents were measured at room temperature using picosecond spectroscopy. These data, and data measured previously in n-alcohols, were compared with Kramers' model using two forms for the friction. When a hydrodynamic model for the friction was used, good agreement was found for the alcohol data only. When the isomerization friction is assumed to scale linearly with the friction for overall reorientational motion, we find excellent agreement for both the alcohol and alkane solvents. In addition, the friction in alkanes is found to be considerably larger than that of alcohols of comparable viscosity. This provides a direct indication that the molecular aspects of the solute–solvent interaction play a role in the barrier crossing process.
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 3056-3061 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The optical reflectivity of fluid interfaces near the critical point is analyzed in the light of recently improved estimates of the surface tension and measurements of the bulk correlation length. In contrast to earlier analyses, it becomes possible to discriminate between the two leading phenomenological theories of fluid interfaces, the intrinsic structure theory originated by Maxwell and van der Waals and the capillary wave theory as developed by Buff, Lovett, and Stillinger. For one of the two systems studied, cyclohexane–methanol, capillary wave theory is found to fit the reflectivity data well, while intrinsic structure theory is in strong disagreement with the reflectivity data. A simple combination of the two theories does not significantly improve the performance of capillary wave theory. For the second system studied, sulfur hexafluoride, neither capillary wave theory nor intrinsic structure theory fits the reflectivity data well, while their combination gives partial agreement with experiment.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 1521-1532 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A phenomenological theory of the liquid wetting layer is presented. Its predictions are compared to those of earlier simpler models as well as to recent experimental results. Special attention is given to the critical region and to the crossover from the complete wetting regime to the critical wetting regime.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 6800-6803 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An analytic expression is derived for the interfacial profile of a liquid–vapor or a liquid–liquid phase equilibrium by assuming, in accord with current ideas, that the equilibrium interface consists of an intrinsic interface of the nonclassical van der Waals type broadened by capillary wave fluctuations. It is shown that in two dimensions of space, the interfacial thickness exhibits a crossover with change of critical exponent from capillary wave behavior at low and near-critical temperatures, to van der Waals behavior at temperatures very close to the critical temperature. The location of the crossover temperature is determined by the ratio of the critical amplitudes of the root-mean squared interfacial thickness and the bulk correlation length. From available experimental data and theory, an estimate of the order of magnitude of the critical amplitude ratio is made, from which the crossover is found to occur in the temperature range 3×10−4 K〈(Tc−T)〈0.3 K. In the currently accessible temperature range, the capillary wave prediction prevails, in contrast to the case of three-dimensional systems.
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  • 10
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 6911-6911 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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