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  • 1
    Electronic Resource
    Electronic Resource
    Ab initio theoretical study on the reactions of a hydrogen molecule with small platinum clusters: A model for chemisorption on a Pt surface (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 5759-5769 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Reactions of a hydrogen molecule with small platinum clusters Ptn (n=1,2,3) are studied theoretically by ab initio methods. This provides a cluster model study for hydrogen chemisorption on a Pt surface. The results suggest that the Pt atom and the linear Pt3 cluster will react with H2 and dissociatively adsorb it, making two Pt–H bonds, whereas the Pt2 cluster will not react with H2 because of a high energy barrier. The dissociative adsorption of a hydrogen molecule occurs at a side-on, on-top site of a surface Pt atom and molecular adsorption does not seem to occur. Essentially only one Pt atom is involved in the initial adsorption process. These findings are in contrast to the palladium case previously reported. Almost no energy barrier exists for the hydrogen migration from one Pt atom to an adjacent one, with a preference being shown for one H atom on each Pt atom rather than two H atoms on one Pt atom. The heat of adsorption, the stability of the catalytic surface, etc., are best represented by the Pt3–H2 system. Spin–orbit coupling effect is examined for the Pt–H2 system and found to be small for the singlet A1 state which is the most important state for the dissociative adsorption. This effect is important, however, to obtain natural potential curve in the large Pt–H2 separation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454534
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  • 2
    Electronic Resource
    Electronic Resource
    Numerical Liouville approach: Formulation of third-order nonlinear optical susceptibilities (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 2986-2995 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: As a continuation of a previous paper [Phys. Rev. A 50, 2989 (1994)], this article develops and describes in detail the new nonperturbative approach to the third-order nonlinear optical susceptibilities χ(3)g(ω) in third-harmonic generation (THG), electric-field-induced second-harmonic generation (EFISH), degenerate four-wave mixing (DFWM), electric-field-induced optical rectification (EFIOR), and electric-field-induced Kerr effect (EFIKE) for N-state quantum systems interacting with intense electric fields. The present method utilizes the Fourier transformation of numerically exact solutions of the Liouville equation, so that it can provide both real and imaginary nonlinear optical spectra valid for arbitrary laser intensities, frequencies, and relaxation. As an application of the method, we investigate the characteristics of nonlinear optical spectra in THG, EFISH, and DFWM for a three-state model that mimics the electronic excited states of t-octatetraene obtained from a full configuration interaction (FCI) calculation using the Pariser–Parr–Pople (PPP) Hamiltonian. Comparisons between the present nonperturbative and the conventional perturbative results are also carried out. The magnitudes of the third-order nonlinear susceptibilities in the off-resonant region show the following trend: χ(3)(THG)(approximately-greater-than)χ(3)(EFISH)(approximately-greater-than)χ(3)(DFWM), with χ(3)(THG) exhibiting the largest frequency dispersion. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468607
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  • 3
    Electronic Resource
    Electronic Resource
    Numerical Liouville approach: Three-type analysis of virtual excitation processes of third-order nonlinear optical spectra in third-harmonic generation (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 2996-3004 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An analysis method based on virtual excitation processes is developed in numerical Liouville approach, which is a new nonperturbative method presented before. In this analysis method (NLA three-type analysis method), third-order nonlinear optical susceptibilities χ(3)g(ω) obtained by the NLA method can be divided into the three-type virtual excitation processes similar to the three-type analysis based on the time-dependent perturbation theory (TDPT three-type analysis). The NLA three-type analysis method is superior to the TDPT three-type analysis one in the points as follows: (1) the NLA three-type analysis can treat the phenomena caused by the intensity-dependent nonlinear susceptibilities including nonperturbative effects and (2) the NLA three-type analysis can divide the resonant nonlinear susceptibilities into three types of virtual excitation processes. In order to explain the procedure of the present analysis, we try to elucidate the characteristics of virtual excitation processes of nonlinear optical spectra in THG for a three-state model that mimics the electronic excited states of a system with noncentrosymmetric charge distribution. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468608
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