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  • 1
    Electronic Resource
    Electronic Resource
    Theory and computational methods for studies of nonlinear phenomena in laser spectroscopy. II. Calculations of steady-state wave functions (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 26 (1984), S. 51-68 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methods will be developed for variational calculations of steady-state wave functions and the corresponding quasienergies. These functions appear as solutions to the time-dependent Schrödinger equation for a molecule interacting with an oscillating electromagnetic field. A variation principle is used to obtain coupled equations for each Fourier component (FC) of the steady-state wave function. The FCs are expanded in configuration state functions using the structure of the complete active space (CAS) SCF approach. Two methods are outlined, one which is based on a common set of molecular orbitals for all FCs and one based on an individual optimization of both CI coefficients and molecular orbitals for each FC. The latter method leads to molecular orbital sets for the different FCs which are mutually nonorthogonal. Formulas are derived for the calculation of higher-order dynamic susceptibilities for steady states. An application is made to the H2 molecule, and results are presented for the frequency-dependent polarizability and hyperpolarizability along the molecular axis. The static values obtained are α = 6.413 (6.387) and γ = 676 (674) atomic units, with exact numbers within parentheses.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560260105
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  • 2
    Electronic Resource
    Electronic Resource
    Theory and computational methods for studies of nonlinear phenomena in laser spectroscopy. I. General formalism (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 26 (1984), S. 35-49 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A general formalism will be outlined, which uses steady-state wave functions for the study of nonlinear phenomena occurring in molecular systems interacting with intense electromagnetic fields. The steady-state approach has the advantage of being free from the secular divergencies and normalization terms which appear in a perturbation expansion of the time-dependent wave function. A physical interpretation of the steady states will be given by considering the interaction between the molecule and the quantized electromagnetic field. The steady states appear as states of the combined system molecule plus electromagnetic field, with eigenvalues corresponding to the energy levels of the combined system in a semiclassical approximation. Evolution operators will be introduced and used to derive formulas for n-photon transition probabilities between molecular states both in the ordinary configuration Hilbert space and in the composite Hilbert space spanned by the steadystate wave functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560260104
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    A mutually consistent procedure for excitation energies and transition densities based on the extended Brillouin's theorem (1993)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 47 (1993), S. 155-173 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A mutually consistent method to calculate excitation energies and corresponding transition densities is proposed. The method is based on the extended Brillouin's theorem that is derived from the nonstationary variation principle. Within the proposed procedure, the Brillouin's conditions, which appear in this extension, are used as a set of nonlinear equations for molecular orbitals and configuration interaction coefficients of the trial ground- and excited-state functions. The excitation energy is an eigenvalue of the set. To some extent, this procedure is related to the variational treatment of the conventional random-phase approximation within the equation-of-motion method. The basic features of the proposed procedure are discussed and it is illustrated by numerical examples. © 1993 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560470207
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  • 4
    Electronic Resource
    Electronic Resource
    Adiabatic perturbation theory for the degenerate case. III. Adiabatic formalism by Gell-Mann and low with an arbitrary switching functionFor part II, see Ref. 5. (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 33 (1988), S. 543-553 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An adiabatic formalism in the degenerate or quasidegenerate subspaces, which does not depend on the particular form of the switching function g(α, t), is outlined. A general factorization theorem for the dynamic operator Sα(t, t0 | g) is proved. This theorem enables one to formulate the perturbation expansion for the effective Hamiltonian and the wave operator which is free from the adiabatic divergencies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560330606
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    Paper (German National Licenses)
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