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  • 1
    Electronic Resource
    Electronic Resource
    Order in chaos and the dynamics and kinetics of unimolecular conformational isomerization (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 3405-3425 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A high degree of structure and therefore order in chaos is found to exist in the detailed dynamical pathways to conformational isomerization. It is shown that this structure can be used to determine the probabilities associated with the dynamical pathways to reaction, trapping, and back reaction. An earlier publication described the mediation of the dynamics of 3-phospholene by phase space structures we called "reactive islands'' (RIS)21. In this paper we extend the physical and mathematical properties of RIS and develop the corresponding kinetic theory. RIS theory is applied to a model of a hindered rotor and 3-phospholene. It is shown that the RIS kinetic model accurately predicts trajectory simulations of conformer population decay. Comparisons with standard RRKM theory are included. A discussion on the extension of RIS theory to quantum reactive dynamics and its relevance to laboratory experiments is also included.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456915
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  • 2
    Electronic Resource
    Electronic Resource
    Reactive islands as essential mediators of unimolecular conformational isomerization: A dynamical study of 3-phospholene (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 3392-3404 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this paper we focus on the detailed nonlinear classical dynamics of conformational isomerization. In particular we concentrate on systems which admit phase space structures we call "reactive islands.'' Our calculations are on a two degree of freedom model of the molecule 3-phospholene with an experimentally fit potential energy surface by Harthcock and Laane. The reactive islands (RIS) are embedded within and are part of chaotic regions of phase space. We find that the RIS are constructed from a linear stability analysis of the period 1 orbit at the transition state or approximated by a similar analysis on reactive periodic orbits. The two approaches converge as the order of the reactive periodic orbit increases. It is found that the fully constructed RIS have well defined regions of reactivity and thus mediate the process of conformational isomerization.The overlap areas of the RIS give important kinetic information such as probabilities for trapped to reactive motion, reactive to trapped motion, and primary back reaction. The implications of this work lie in precisely identifying the microscopic dynamical pathway for isomerization. The results of this work and its relation to the related work of Gray and Rice as well as its relation to contemporary work in modern dynamics is also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456914
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  • 3
    Electronic Resource
    Electronic Resource
    The Fourier grid Hamiltonian method for bound state eigenvalues and eigenfunctions (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 3571-3576 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new method for the calculation of bound state eigenvalues and eigenfunctions of the Schrödinger equation is presented. The Fourier grid Hamiltonian method is derived from the discrete Fourier transform algorithm. Its implementation and use is extremely simple, requiring the evaluation of the potential only at certain grid points and yielding directly the amplitude of the eigenfunctions at the same grid points.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456888
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  • 4
    Electronic Resource
    Electronic Resource
    Photodissociation dynamics and emission spectroscopy of H2S in its first absorption band: A time dependent quantum mechanical study (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 6520-6534 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A theoretical study of the photodissociation dynamics of H2S in its first absorption band is presented. The potential energy surfaces underlying the dynamics of the breakup process have been modeled so as to reproduce the principal features of all the available experimental data. The modeling is performed using time dependent quantum dynamical methods and involves the exact numerical solution of the time dependent Schrödinger equation. The fitting of the experimental observations requires the use of potential energy surfaces corresponding to two excited electronic states. We have been able to determine two such surfaces which reproduce the observed structure in the absorption spectrum, the main features of the emission spectrum of the dissociating molecule, and the vibrational distribution of the HS photofragments. The calculations utilize a recently developed method for analyzing the wave packet dynamics to extract the partial photodissociation cross sections. The photodissociation process is found to be consistent with an initial excitation to a single excited dissociative diabatic electronic state which is weakly coupled to another, whose principal role within the first absorption band is to introduce diffuse structure into the absorption spectrum and minor perturbations to the nuclear motion. The motion on the principal dissociative electronic surface is dominated by that in the two bond stretching coordinates, while that on the surface of the second perturbing state is a one dimensional vibrational motion which may correspond to either symmetric stretching or bending, but is most probably a complex combination of both. A new method is presented for performing the time dependent quantum mechanical calculation on two coupled potential energy surfaces when the motions on both surfaces are treated in a reduced dimensionality and the dynamically active coordinates on the two surfaces are different.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459678
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  • 5
    Electronic Resource
    Electronic Resource
    Resonances in the chaotic regime. Interpretation in terms of periodic orbits (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 8456-8467 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A method using classical mechanics to identify exact resonance eigenstates of a reactive scattering system is presented. Semiclassical approximate eigenstates are first constructed from classical trajectories of a defining topology. The semiclassical wave functions then serve as initial states for an exact quantum time-dependent wave packet propagation. The quality of the initial semiclassical approximation is readily apparent from the extent to which the spectrum of the resulting dynamics is dominated by a single peak. The systematic construction of the resonant eigenstate spectrum in association with a progression through defining classical topologies is emphasized, and the predictive implications of the method for approximating essential resonant eigenstate nodal structure and energies are discussed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470156
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  • 6
    Electronic Resource
    Electronic Resource
    Semiclassical theory of resonances in 3D reactions. II. Resonant quasiperiodic orbits for F+H2 (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 3390-3401 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Numerical methods for the computation and semiclassical quantization of resonant orbits (to accurately predict resonance energies of the 3D, J=0, F+H2 reaction) are extended from the periodic trajectories of part I to the more general quasiperiodic trajectories. In addition, semiclassical quantization conditions are revised for application to newly discovered collinear resonant periodic orbits and comparative stability analysis is used to evaluate the relative significance of these alternative orbits for both the collinear and 3D reactions. The method used in this series for computing the bound classical trajectories is then compared with the more general RP method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449144
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  • 7
    Electronic Resource
    Electronic Resource
    Time-dependent quantum dynamics of reactive scattering and the calculation of product quantum state distributions — A study of the collinear F+H2(v=0) → HF(v′)+H reaction (1991)
    Springer
    Theoretical chemistry accounts 79 (1991), S. 313-322 
    Details
    ISSN: 1432-2234
    Keywords: Partial cross sections ; Time-dependent quantum theory ; Resonance behaviour ; Reactive scattering resonances
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new method for the calculation of partial cross sections in the time-dependent quantum theory of molecular reactive scattering processes is discussed. Preliminary calculations are presented which clearly illustrate the power of the method. They show how all the partial cross sections associated with a single initial quantum state may be computed over a very wide energy range from a single propagation of a prepared wavepacket. The resonance behaviour is obtained without difficulty and the energies of the reactive scattering resonances are exactly reproduced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01113699
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  • 8
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    Resonances in the chaotic regime. Interpretation in terms of periodic orbits (1995)
    American Institute of Physics
    Details
    Publication Date: 1995-11-15
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
    Published by American Institute of Physics
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  • 9
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    The Fourier grid Hamiltonian method for bound state eigenvalues and eigenfunctions (1989)
    American Institute of Physics
    Details
    Publication Date: 1989-09-15
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
    Published by American Institute of Physics
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  • 10
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    Order in chaos and the dynamics and kinetics of unimolecular conformational isomerization (1989)
    American Institute of Physics
    Details
    Publication Date: 1989-09-15
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
    Published by American Institute of Physics
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