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  • 1
    Electronic Resource
    Electronic Resource
    The MIME effect: absence of normal modes corresponding to vibronic spacings (1982)
    s.l. : American Chemical Society
    Inorganic chemistry 21 (1982), S. 3858-3859 
    Details
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ic00140a057
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  • 2
    Electronic Resource
    Electronic Resource
    Accurate First Principles Calculation of Molecular Charge Distributions and Solvation Energies from Ab Initio Quantum Mechanics and Continuum Dielectric Theory (1994)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 116 (1994), S. 11875-11882 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00105a030
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  • 3
    Electronic Resource
    Electronic Resource
    Jahn-Teller effects in the photodissociation of ozone (1989)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 111 (1989), S. 2772-2776 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00190a005
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  • 4
    Electronic Resource
    Electronic Resource
    Symmetry adapted Fourier solution of the time-dependent Schrödinger equation (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 2517-2525 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The application of the time-dependent Schrödinger equation/Fourier method to triatomic systems in hyperspherical coordinates is described. In particular, we consider the high symmetry situation of three identical particles, and focus on the reduced dimensional dynamics in the hyperspherical coordinate χ, which contains all the symmetry of the general problem. The periodic structure of the wave functions in the χ coordinate leads to a discrete spectrum in k space. The additional finite symmetry of the wave functions in this coordinate gives rise to selection rules, analogous to rotational selection rules for symmetric top molecules, which ensure that only one out of six of these integer k values has nonzero intensity. It is possible to reduce the range of the wave function (and the calculation) by a factor of 6 by selecting only one replica of the coordinate space wave function. The FFT automatically increases the spacing in k space by a factor of 6, eliminating the lines in k space with nonzero amplitude. For each different symmetry of wave function in coordinate space it is necessary to shift the compacted grid in k space by a different amount, in accord with k space selection rules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457943
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  • 5
    Electronic Resource
    Electronic Resource
    CH2I2 photodissociation: Dynamical modeling (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 3602-3611 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A full quantum mechanical calculation is carried out on the first excited state of CH2I2 to model the absorption and emission spectra and examine the photodissociation dynamics from a time dependent point of view. The dissociation at 355 nm is direct in the sense that the wave packet does not revisit the Franck–Condon region. The initial motion of the excited molecule is mainly along the CI2 symmetric stretch coordinate while simultaneously spreading in the antisymmetric stretch coordinate. The molecule then dissociates along a C–I "local'' mode; no I2 can be formed in this energy region. Vibrationally hot CH2I radical in the C–I mode is predicted. The model is in good agreement with available experimental results. A simple and intuitive method is presented to construct model potential energy surfaces for two chromophore systems from the potential energy surface and information known for the corresponding single chromophore. CH3I and CH2I2 are used as numerical illustrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454880
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  • 6
    Electronic Resource
    Electronic Resource
    Photoabsorption and photoemission of ozone in the Hartley band (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 6667-6675 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Theoretical calculations of ozone photoabsorption and photoemission in the Hartley band are presented. The potential energy surfaces of Sheppard and Walker [J. Chem. Phys. 78, 7191 (1983)] and of Barbe et al. [J. Mol. Spectrosc. 49, 171 (1974)] are used for the excited (1B2) and ground (1A1) states, respectively. In contrast with several recent studies, large amplitude motion in the symmetric and asymmetric stretch coordinates is explicitly included. Qualitative agreement is obtained with the experimental emission spectrum at 266 nm, although some discrepancies persists, using either the original Sheppard–Walker surface or various modifications thereof. Moreover, the calculations do not reproduce the experimentally observed structure atop the Hartley absorption band, eliminating some possibilities for the origin of this structure. The photofragmentation dynamics was computed by numerical integration of the time-dependent Schrödinger equation on a two-dimensional grid, and spectral observables were recovered via Fourier transform.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455339
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  • 7
    Electronic Resource
    Electronic Resource
    Ammonia: Dynamical modeling of the absorption spectrum (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 5919-5934 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A quantum mechanical calculation involving a time-dependent formalism is used to study the A˜–X˜ transition in ammonia. The experimental spectrum exhibits a single progression in the bend despite evidence that there is a displacement in both the bond lengths and bond angles in going from the ground to first excited state. Two models for the excited state surface are presented which reproduce this single progression in the bend. The starting point for our study is an ab initio surface. The excited state surface is first adjusted to match the equilibrium geometries and rotational constants derived from experiment. The surface is then further refined to produce agreement with the experimental absorption and emission frequency and intensity patterns.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458362
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  • 8
    Electronic Resource
    Electronic Resource
    Time dependent quantum mechanics using picosecond time steps: Application to predissociation of HeI2 (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 3403-3409 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Time-dependent quantum mechanics has proved to be a useful conceptual and calculational tool for a wide range of femtosecond time scale processes. In this paper we develop a method of extending time-dependent methodology to processes taking many picoseconds, through use of the interaction representation of quantum mechanics. Two implementations are presented, one in the energy frame and one in the coordinate frame; both of these implementations scale as N2 with the number of basis functions, as opposed to N3 for a matrix diagonalization. The interaction representation approach allows the use of time steps much greater than those that can be used in the Schrödinger representation, and is expected to be useful for the broad class of problems where the Hamiltonian can be partitioned into H0+V, where V(very-much-less-than)H0. Converged quantum mechanical results are presented for the predissociation of T-shaped HeI2 from highly excited vibrational levels, for times up to 200 ps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457851
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  • 9
    Electronic Resource
    Electronic Resource
    Chemical branching in two chromophore systems: Application to the photodissociation of C2F4IBr (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 2324-2332 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Time dependent quantum mechanical calculations of the photodissociation of C2F4IBr are reported. The calculations successfully model the experimental absorption spectra [W. H. Pence, S. L. Baughcum, and S. R. Leone, J. Phys. Chem. 85, 3844 (1981)] as well as the branching ratio of final products due to photodissociation [D. Krajnovich, L. J. Butler, and Y. T. Lee, J. Chem. Phys. 81, 3031 (1984)]. The model used consists of two degrees of freedom, an iodine and a bromine coordinate, and two diabatic potential energy surfaces which are repulsive in the iodine and bromine cordinates, respectively. The study gives a consistent picture of the experimental I:Br branching ratio at 266, 248, and 193 nm in terms of a crossing of diabatic potential energy surfaces. However, the same model requires an anomalously small surface coupling when applied to the related CH2IBr system to agree with experiment. The time dependent formulation of absorption spectroscopy and photodissociation is extended to systems with chemical branching, and a simple new technique for calculating frequency dependent chemical branching ratios from short time dynamics is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457040
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  • 10
    Electronic Resource
    Electronic Resource
    Control of selectivity of chemical reaction via control of wave packet evolution (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 5013-5018 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A time-dependent formulation of two-photon spectroscopy is employed to show that selectivity of reactivity can be achieved via coherent two-photon processes. The problem of finding the optimum waveform (i.e., coherent pulse sequence) that will maximize the formation of a desired chemical species is formulated as a problem in the calculus of variations, and solved for two different cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449767
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