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  • 1
    Electronic Resource
    Electronic Resource
    The dynamics of proton transfer in H5O2+ (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 8461-8468 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We perform high-level, quantum molecular dynamics simulations of proton transfer in the protonated water dimer, H5O2+. The electronic structure of the system is calculated concurrently with the nuclear motion using Born–Oppenheimer molecular dynamics plus density functional theory. Performing the calculations at finite (thermal) temperatures allows us to observe and quantify such effects as the broadening of the electronic density of states, the thermal splitting of degenerate states, the shift of the highest occupied molecular orbital, the thermal expansion of the dipole moment, and the thermal shift, coupling and broadening of the vibrational density of states. At two of the temperatures considered (225 K and 360 K), we find that H5O2+ exists in a dynamical equilibrium state in which the proton oscillates between two water molecules. The characteristic frequencies of the proton motion are very sensitive to temperature. At 40 K and 225 K, strong peaks are identified in the vibrational spectrum corresponding to the motion of the proton between the two oxygen atoms. At 360 K, the frequencies of this motion are distributed among a series of peaks between 1100 and 1800 cm−1. At all temperatures investigated, the proton motion is coupled strongly to other degrees of freedom in the water molecules and the dimer. Statistically, the proton is localized near one of the two H2O molecules to form H3O+ with a probability of 0.09 at 225 K, and 0.18 at 360 K. At low temperature (40 K), the proton remains localized near the midpoint of the two oxygens, and has almost zero probability to exist as H3O+. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475046
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  • 2
    Electronic Resource
    Electronic Resource
    Structure and dynamics of the S3 state of CS2 (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 6570-6576 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a detailed theoretical investigation of the structure and dynamics of the S3 excited state of CS2. The excited state is treated using equation-of-motion coupled-cluster (EOM-CC) theory, and analytic gradients are used in determining the vibrational frequencies. Information from the structure calculations is used to construct a model potential surface. Time-dependent wave packet methods are used to generate the transition state spectrum corresponding to collinear CS2. The spectrum is comprised of transition state resonances which are assigned via a spectral quantization method. The energies and lifetimes of the spectral features are related to recent experimental measurements. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474899
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  • 3
    Electronic Resource
    Electronic Resource
    Spectral quantization of transition state dynamics for the three-dimensional H+H2 reaction (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 1725-1729 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Applying a spectral quantization method, we find the positions and widths of 32 transition state resonances in the three-dimensional reaction H+H2 with J=0. The assignment of many of the resonances appears to follow asymmetric stretch and bend progressions for a linear triatomic molecule.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467728
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  • 4
    Electronic Resource
    Electronic Resource
    Controlling the Future of Matter (1995)
    s.l. : American Chemical Society
    Accounts of chemical research 28 (1995), S. 133-140 
    Details
    ISSN: 1520-4898
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ar00051a006
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  • 5
    Electronic Resource
    Electronic Resource
    Electron correlation in the ground and low-lying excited states of alkaline earth atoms (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 5153-5162 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Variational wave functions are constructed for the ground and several low-lying excited states of the alkaline earth atoms Be, Mg, Ca, Sr, and Ba. Effective core potentials are employed to treat these atoms as pseudo-two-electron systems. Conditional probability distributions ρ(r2,θ12||r1=ζ), representing the probability of finding one electron at a distance r2 from the nucleus with interelectronic angle θ12, given that the other electron is at a distance r1 from the nucleus, are plotted for several states of the alkaline earths at various values of ζ. We find that the molecular model which so successfully classifies and describes the collective rotational and vibrational states of doubly excited He carries over well to these ground and low-lying states of the lighter alkaline earths. For the heavier atoms, though the angular correlation remains strong, the application of the molecular model becomes less clear. Some states exhibit behavior intermediate between independent particle-like and collective, and "interloper states'' appear which have no immediate interpretation in terms of a single vibrator-rotator model or relationship to the states of doubly-excited helium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449727
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  • 6
    Electronic Resource
    Electronic Resource
    Periodic Hartree–Fock study of the adsorption of molecular oxygen on a reduced TiO2 (110) surface (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 4798-4810 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a theoretical analysis of O2 adsorption on a reduced TiO2 (110) rutile surface, based on periodic ab initio Hartree–Fock calculations. Three different orientational approaches, three different spin symmetries, and two different adsorption sites are considered. We also consider the possibility that the surface can absorb more than one oxygen molecule. Positions of the surface ions, oxygen ions belonging to the third and fourth layers of the slab, and the bond lengths of the O2 and O2-substrate distances are optimized. Adsorption energies, admolecule-substrate bond lengths, spin densities and Mulliken charges are analyzed. The model is tested by comparing spin densities and relaxation parameters obtained for the reduced TiO2 (110) system to previous theoretical results. Finally, we discuss the relationship of our results to experimental observations of thermal desorption rates at low temperatures (100–600 K). © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1394203
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  • 7
    Electronic Resource
    Electronic Resource
    Optical control of molecular dynamics: Molecular cannons, reflectrons, and wave-packet focusers (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 6562-6578 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We consider the control of molecular dynamics using tailored light fields, based on a phase space theory of control [Y. J. Yan et al., J. Phys. Chem. 97, 2320 (1993)]. This theory enables us to calculate, in the weak field (one-photon) limit, the globally optimal light field that produces the best overlap for a given phase space target. We present as an illustrative example the use of quantum control to overcome the natural tendency of quantum wave packets to delocalize on excited state potential energy curves. Three cases are studied: (i) a "molecular cannon'' in which we focus an outgoing continuum wave packet of I2 in both position and momentum, (ii) a "reflectron'' in which we focus an incoming bound wave packet of I2, and (iii) the focusing of a bound wave packet of Na2 at a turning point on the excited state potential using multiple light pulses to create a localized wave packet with zero momentum. For each case, we compute the globally optimal light field and also how well the wave packet produced by this light field achieves the desired target. These globally optimal fields are quite simple and robust. While our theory provides the globally optimal light field in the linear, weak field regime, experiment can in reality only provide a restricted universe of possible light fields. We therefore also consider the control of molecular quantum dynamics using light fields restricted to a parametrized functional form which spans a set of fields that can be experimentally realized. We fit the globally optimal electric field with a functional form consisting of a superposition of subpulses with variable parameters of amplitude, center time, center frequency, temporal width, relative phase, and linear and quadratic chirp. The best fit light fields produce excellent quantum control and are within the range of experimental possibility. We discuss relevant experiments such as ultrafast spectroscopy and ultrafast electron and x-ray diffraction which can in principle detect these focused wave packets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465848
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  • 8
    Electronic Resource
    Electronic Resource
    Quantum-mechanical calculations of the dissociation of H3 Rydberg states (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 4283-4292 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present three-dimensional, time-dependent quantum-mechanical calculations of the dynamics of the dissociation of H3 Rydberg states at total energies up to 6 eV. The method used in this work employs a Chebychev propagator in time, and computes the kinetic-energy operators in the discrete variable representation. We calculate the total dissociation cross section, as well as partial vibrational and rotational cross sections, and compare our results to previous two-dimensional calculations and to experiment. The results display clear three-dimensional effects, and indicate the importance of including both sheets of the H3 ground potential-energy surface in the dynamics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462822
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  • 9
    Electronic Resource
    Electronic Resource
    Coherent control of bimolecular chemical reactions (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 1126-1131 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We show how the method of coherent control can be applied to control product yield in bimolecular chemical reactions. First, a laser pulse prepares a coherent superposition of two bound levels of an electronically excited state of the reactants. Then, after a variable delay, a second laser pulse photodissociates the system to the ground state continuum. By varying the detuning of the excitation pulse and the delay between the two pulses, we show that significant control of the product ratio can be achieved. As a first application of the method we demonstrate, with exact quantum-mechanical calculations, the control of the collinear H+H2 and D+H2 reactions. The pulses and delays used in these calculations are on the order of picoseconds, a range of time scales well within that achievable with conventional laser systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458174
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  • 10
    Electronic Resource
    Electronic Resource
    An exact coupled-channel study of the transition state spectroscopy of the collinear H+H2 reaction (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 6401-6408 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present an exact coupled-channels method for calculating free-bound transition dipole amplitudes in reactive chemical systems. The method employs a log-derivative propagator in hyperspherical coordinates and the artificial channel method to calculate the desired integrals implicitly. We apply this method to a study of the transition state spectroscopy of the collinear H+H2 reaction, analyzing in detail the effect of the reactive Feshbach resonances on the spectra. A statistical analysis of the spectral intensity fluctuations shows that at low collision energies the intensity distribution is poorly fit by the Porter–Thomas distribution. As the collision energy increases, the fit becomes very good, indicating strongly coupled degrees of freedom. These results indicate the importance of considering the preparation of the initial state when performing statistical analyses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456306
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