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  • 1
    Electronic Resource
    Electronic Resource
    Beyond the time-dependent Hartree grid approximation for curve-crossing problems (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 3613-3623 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new "configuration-interaction'' method is presented which extends the single-surface time-dependent Hartree grid (TDHG) approximation into a formally exact algorithm for obtaining multidimensional quantum wave-packet dynamics on nonradiatively coupled electronic potential surfaces. As a numerical example, photofragmentation cross sections are computed for a two-degree-of-freedom model of direct dissociation. For systems prepared in vibrationally excited states of the ground electronic potential the TDHG approximation fails due to "direct correlation'' effects, while our method provides accurate results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461914
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  • 2
    Electronic Resource
    Electronic Resource
    Application of a coupled-surface time-dependent Hartree grid method to excited state optical spectroscopy (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 2773-2780 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dynamics of multidimensional wave packet motion on nonadiabatically coupled electronic potential surfaces is explored by numerically exact time-dependent quantum mechanics and by the time-dependent Hartree grid (TDHG) approximation. Excellent agreement is found between the TDHG and the exact evolution of the wave packet; in particular, the approximation yields accurate total cross sections for electronic absorption, excitation profiles for resonance Raman scattering, and partial cross sections for photofragmentation in a two degree of freedom model of direct dissociation (which is qualitatively related to experimentally observed processes in methyl halides and ICN).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459854
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  • 3
    Electronic Resource
    Electronic Resource
    Adding configuration interaction to the time-dependent Hartree grid approximation (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 4740-4749 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The time-dependent Hartree grid (TDHG) method is extended into an ab initio algorithm for obtaining exact quantum wave packet dynamics. The new algorithm employs a superposition of orthogonal zeroth order time-dependent basis functions generated from a single TDHG wave packet trajectory. The superposition coefficients are themselves time-dependent, and are responsible for mixing the basis functions in such a way as to represent exact solutions of the time-dependent Schrodinger equation. Evolution of the superposition coefficients is governed by a set of first-order linearly coupled ordinary differential equations. The couplings between coefficients are given by matrix elements of a naturally identified interaction potential taken between members of the zeroth order basis. In numerical tests involving computation of S-matrix elements for collinear inelastic atom–Morse oscillator scattering the method proves accurate, flexible and efficient, and appears to be easily extendable to more complicated systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458664
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  • 4
    Electronic Resource
    Electronic Resource
    Erratum: Application of a coupled-surface time-dependent Hartree grid method to excited state optical spectroscopy [J. Chem. Phys. 94, 2773 (1991)] (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 1430-1431 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461077
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  • 5
    Electronic Resource
    Electronic Resource
    Application of the time-dependent Hartree grid–configuration interaction method to the desorption of diatomic molecules from solid surfaces (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 9629-9636 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We study UV laser induced photodesorption of diatomic molecules from solid surfaces by means of the time-dependent Hartree grid–configuration interaction (TDHG–CI) method [J. Chem. Phys. 93, 4740 (1990)]. Converged partial and total absorption cross sections are computed in several cases to demonstrate the flexibility and accuracy of the method. Comparison to TDHG results without CI corrections is also made. The failure of simple TDHG dynamics to reproduce state resolved rotational cross sections in various strong coupling limits is noted as a justification for the development of TDHG–CI algorithms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465496
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  • 6
    Electronic Resource
    Electronic Resource
    Time-dependent Hartree configuration interaction study of the ICN photodissociation dynamics (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 8016-8024 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The application of the time-dependent Hartree configuration interaction (TDH-CI) method is examined for the ICN photodissociation process. Corrections to the approximate TDH dynamics are included up to a quantitative agreement with exact results. The validity of the TDH approximation, for computing some averaged magnitudes, is also tested against exact results. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471519
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  • 7
    Electronic Resource
    Electronic Resource
    Liquid EXAFS cells for measurements in transmission and fluorescence mode of corrosive samples (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2153-2154 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The design of two small, compact and portable cells for EXAFS measurements of liquids is presented. One of the cells has been optimized for transmission measurements and the other for fluorescence. The sample chamber of both cells has been designed metal free to avoid corrosion by acids or bases. Materials and construction of the cell are such that their cost is quite low. The cells have been tested by recording EXAFS spectra of ionic aqueous solutions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144718
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  • 8
    Electronic Resource
    Electronic Resource
    Examining the influence of the [Zn(H2O)6]2+ geometry change on the Monte Carlo simulations of Zn2+ in water (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 5968-5970 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Quantum chemical calculations have been carried out to estimate the variation in the interaction energy between one or two water molecules and the Zn2+ hydrated ion ([Zn(H2O)6]2+) when the Zn–O intramolecular distance is changed. Likewise, changes in the interaction energy between a second hydration shell formed by twelve H2O and the hydrated ion when shrinking the hexahydrate have been also examined, using a previously reported hydrated ion–water potential [Pappalardo et al., J. Phys. Chem. 97, 4500 (1993)] and the Matsuoka–Clementi–Yoshimine (MCY) potential for the water–water interactions. Using these potentials and that of Clementi for the Zn2+–H2O interaction, Monte Carlo simulations have been performed using two different Zn–O distances for the first hydration shell. Results show that influence of the geometrical relaxation on the solvation energy is not large, about 2.5%. Consequences on the use of a flexible or rigid hydrated ion are discussed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472453
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  • 9
    Electronic Resource
    Electronic Resource
    Coupling a polarizable water model to the hydrated ion–water interaction potential: A test on the Cr3+ hydration (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 2339-2347 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A strategy to build interaction potentials for describing ionic hydration of highly charged monoatomic cations by computer simulations, including the polarizable character of the solvent, is proposed. The method is based on the hydrated ion concept that has been previously tested for the case of Cr3+ aqueous solutions [J. Phys. Chem. 100, 11748 (1996)]. In the present work, the interaction potential of [Cr(H2O6)]3+ with water has been adapted to a water model that accounts for the polarizable character of the solvent by means of a mobile charge harmonic oscillator representation (MCHO model) [J. Chem. Phys. 93, 6448 (1990)]. Monte Carlo simulations of the Cr3+ hexahydrate plus 512 water molecules have been performed to study the energetics and structure of the ionic solution. The results show a significant improvement in the estimate of the hydration enthalpy [ΔHhydr(Cr3+)=−1109.6±70 kcal/mol] that now matches the experimental value within the uncertainty of this magnitude. The use of the polarizable water model lowers by ∼140 kcal/mol the statistical estimation of the [Cr(H2O6)]3+ hydration enthalpy compared to the nonpolarizable model. (−573 kcal/mol for the polarizable model vs −714 kcal/mol for the nonpolarizable one.) This improvement reflects a more accurate treatment of the many-body nonadditive effects. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480799
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  • 10
    Electronic Resource
    Electronic Resource
    Shape and size of simple cations in aqueous solutions: A theoretical reexamination of the hydrated ion via computer simulations (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 1669-1676 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The simplest representation of monoatomic cations in aqueous solutions by means of a sphere with a radius chosen on the basis of a well-defined property (that of the bare ion or its hydrate) is reexamined considering classical molecular dynamics simulations. Two charged sphere–water interaction potentials were employed to mimic the bare and hydrated cation in a sample of 512 water molecules. Short-range interactions of trivalent cations were described by Lennard-Jones potentials which were fitted from ab initio calculations. Five statistically independent runs of 150 ps for each of the trivalent spheres in water were carried out in the microcanonical ensemble. A comparison of structural and dynamical properties of these simple ion models in solution with those of a system containing the Cr3+ hydrate ([Cr(H2O)6]3+) is made to get insight into the size and shape definition of simple ions in water, especially those that are highly charged. Advantages and shortcomings of using simple spherical approaches are discussed on the basis of reference calculations performed with a more rigorous hydrated ion model [J. Phys. Chem. B 102, 3272 (1998)]. The importance of nonspherical shape for the hydrate of highly charged ions is stressed and it is paradoxically shown that when spherical shape is retained, the big sphere representing the hydrate leads to results of ionic solution worse than those obtained with the small sphere. A low-cost method to generate hydrated ion–water interaction potentials taking into account the shape of the ionic aggregate is proposed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477808
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