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  • 1
    Electronic Resource
    Electronic Resource
    The time propagation of the stationary states of a Morse oscillator by the Gaussian wave packet method (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 3060-3070 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Gaussian wave packet method has been developed for the simulation of processes like molecular collisions, photodissociation of molecules, and laser excitations of molecules. So far a necessary condition for an accurate result is that the fragment states are propagated accurately. We have considered one-dimensional bound states described by a Morse potential, and carried out a systematic study of the ability of the Gaussian wave packet method to propagate the stationary states. It is found that the complete set of equations of motion as derived by the minimum error method (MEM) cannot be used in practical calculations because of numerical problems. These are eliminated by the introduction of simplifications such as the independent Gaussian approximation (IGA), where each wave packet is propagated independently. The conditions for an accurate propagation within that assumption are developed, and a simple method is devised to identify those states, which are propagated accurately. This procedure may be used to investigate when the Gaussian wave packet method is appropriate for the simulation of a given process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455909
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  • 2
    Electronic Resource
    Electronic Resource
    Fourier transform linewidths measurements in NH3 in the vibrational ground state (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 5373-5376 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have measured linewidths of several pure rotational transitions in the vibrational ground state in the far infrared (80–200 cm−1 ). The experiments were conducted by using a Fourier transform spectrometer and gases (NH3 diluted by H2 or He) contained in a 15 cm absorption cell at room temperature. The aim of our study is to discuss the vibrational effect by comparing our measurements with those done in the infrared, 3 and 6 μm regions (ν3 and ν4 bands) and to find evidence for vibrational dependence. The measured pressure broadening cross sections were typically found to be 26 A(ring)2 for the NH3 –H2 collisions and 16 A(ring)2 for the NH3 –He collisions, by comparing these values with those obtained for the ν4 mode, 35 A(ring)2 for the H2 perturber and 17 A(ring)2 for the He perturber, we see a vibrational effect for the NH3 –H2 collisions but not significant for the NH3 –He ones. Our measurements are in good agreement with the theoretical calculations done by Billing by using the semiclassical coupled states method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455588
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  • 3
    Electronic Resource
    Electronic Resource
    A classical path approach to reactive scattering. I. Use of hyperspherical coordinates (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 4779-4787 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A classical path method is described for treating reactive collisions in three-body systems. The key feature of the method is the use of hyperspherical coordinates, which allow the definition of classical and quantum subsystems in such a way as to be independent of the arrangement of the particles. The "relative'' motion and overall rotation are treated classically, while the "arrangement'' and internal motion are treated quantum mechanically. The method is applied to the collinear D+HH system on the PK2 potential energy surface. These calculations show a great improvement over quasiclassical trajectory results in the vicinity of the apparent threshold of the reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454724
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  • 4
    Electronic Resource
    Electronic Resource
    A classical path approach to reactive scattering. II. Apparatus for three-dimensional applications (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 6830-6838 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We describe the apparatus necessary for the application of a previously reported classical path method to three-dimensional reactive collisions. The case of D+H2 is used as an example.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457352
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  • 5
    Electronic Resource
    Electronic Resource
    Pressure broadening and cross relaxation of ammonia perturbed by hydrogen and helium: Implications on intermolecular potentials and discussion of rotational effects (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 1551-1556 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The study of the absorption line profiles in the infrared region (6–7 μm), by means of a diode laser spectrometer and a FT spectrometer in ammonia diluted in He and H2 at room temperature, allowed us to determine pressure broadening cross section and the intradoublet inelastic rate (due to molecular inversion).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454134
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  • 6
    Electronic Resource
    Electronic Resource
    Quantum dressed classical mechanics (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 6641-6653 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have formulated a new way of making quantum corrections to classical mechanics. The method is based on a time-dependent discrete variable representation (DVR) of the wave function with grid points defined by the Hermite part of a basis set, the Gauss–Hermite basis set. The formulation introduces a set of grid points which follow the classical trajectory in space. With enough trajectories (DVR-points) the method approaches the exact quantum formulation. With just a single grid point in each dimension, we recover classical mechanics. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1357787
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Vibrational relaxation in the NO+–He collision system: Implication of the Gislason–Ferguson model (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 6669-6674 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The rate constants for vibrational relaxation of NO+ in collisions with He are calculated using the semiclassical (classical path) approach of Billing and the interaction potentials, constructed by us on the base of the model of Gislason and Ferguson. An encouraging agreement of the theoretical results with near thermal selected ion flow drift tube data is achieved. The role of the anisotropy of the interaction potential in the vibrational relaxation process is also investigated. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469140
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  • 8
    Electronic Resource
    Electronic Resource
    Erratum: Integral cross sections and rate constants for the reaction OH+H2→H2O+H: A semiclassical wave packet approach [J. Chem. Phys. 101, 2785 (1994)] (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 1102-1102 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469572
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  • 9
    Electronic Resource
    Electronic Resource
    Semiclassical calculation of cross sections for vibration–rotation energy transfer in HF–HF collisions (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 2593-2603 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Cross sections for HF(10)+HF(00) → HF(v1 j1)+HF(v2 j2) are calculated using a semiclassical method in which the relative translational motion is treated classically, whereas the vibrational and rotational motion of both molecules are quantized. In order to decouple the rotation projection states we introduce the large j approximation in the coupling elements. The results of 98-quantum state calculations at three energies are reported and qualitatively compared with recent laser experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450329
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  • 10
    Electronic Resource
    Electronic Resource
    Integral cross sections and rate constants for the reaction OH+H2→H2O+H: A semiclassical wave packet approach (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 2785-2792 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A semiclassical wavepacket method has been introduced to study diatom–diatom exchange reactions of the type AB+CD→ABC+D; ABD+C using purely inelastic coordinates. The vibrations of the two reagent molecules are treated quantum mechanically by an exact solution of the time-dependent Schrödinger equation. The rotational motions as well as the relative translational motion of the two molecules are treated classically. The coupling between the quantal and classical degrees of freedom is described within an effective Hamiltonian approach. The method has been illustrated for the exothermic reaction OH+H2→H2O+H by computing integral cross sections and rate constants. The computed integral cross sections are in reasonable accord with existing quasiclassical trajectory results, but in significant disagreement with recently reported approximate quantum mechanical calculations. The calculated rate constants for the ground vibrational states of the reagents are in good agreement with experimental rate constants in the temperature range 300≤T≤700 K. Comparisons of the rate constants are also made with various theoretical results, including a recently reported six-dimensional quantum mechanical calculation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468469
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    Paper (German National Licenses)
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