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  • 1
    Electronic Resource
    Electronic Resource
    Spectroscopy and photodissociation dynamics of H2O: Time-dependent view (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 1666-1676 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a study of H2O photodissociation dynamics in the first excited state. The absorption and emission spectra are calculated quantum mechanically using a time-dependent wave packet propagation technique. The excited state potential energy surface is obtained from ab initio data generated by Palma et al., while the ground state is a model by Reimers and Watts cast in a simple analytical form and constructed by fitting to infrared data. The variation of the transition dipole moment is taken into account by using an analytical functional form which is adjusted to fit the low resolution experimental emission spectrum. The calculated absorption spectrum is very similar to both the experimental one and results obtained with other methods. The high resolution emission spectrum is calculated for the first time and shows excellent agreement with the recently measured experimental spectrum by Hudson and co-workers. Dynamics on both the ground and excited states are examined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456060
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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    The first absorption band for H2O: Interpretation of the absorption spectrum using time dependent pictures (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 5607-5613 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We examine the relation between photodissociation dynamics and the form of the total absorption spectrum for H2O in the first absorption band. Application of an exact time dependent formalism gives a direct and intuitive relation between molecular motion and spectral features. We show that the series of weak structures on top of the broad continuum is due to symmetric stretch motion in the excited state. The spacing between the structures is, essentially, given by the frequency associated with this motion. In addition, we present some excited state eigenfunctions, which provide a direct connection between the structured spectrum, the final product distributions, and the dynamics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455567
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  • 4
    Electronic Resource
    Electronic Resource
    CH2I2 photodissociation: Emission spectrum at 355 nm (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 309-313 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The emission spectrum from photodissociating CH2I2 excited at 355 nm is presented. Interpretation of the data is given in a time dependent picture. The progression on the CI2 symmetric stretch and even quanta in the antisymmetric stretch indicate initial motion during dissociation along the symmetric stretch coordinate and subsequent spreading in the antisymmetric stretch coordinate. The moderately strong bending fundamental suggests that the bond angle changes when the molecule is promoted from the ground to the excited state. Both dynamics and the geometry near the Franck–Condon region on the excited surface are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455471
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  • 5
    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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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Hybrid mechanics. II (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 7317-7329 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We recently published a new method for the calculation of the time evolution of a wave function. We used an accurate approximate method to calculate the time propagator for a finite time Δt. Numerical calculations showed that this scheme works quite accurately, but that it is not more efficient than conventional methods. In this paper we propose to use a very fast and simple, but less accurate semiclassical method for the calculation of the time propagator. The approximation consists in the replacement of the Hamiltonian by a quadratic approximation around the center of the evolving wave packet called thawed Gaussian dynamics. We show by numerical examples in one and two dimensions that, despite this crude approximation, we achieve nearly the same accuracy as in the foregoing paper, but with an efficiency that is typically more than an order of magnitude better. We further show that the method is able to describe tunneling and long time dynamics (e.g., 1000 vibrational periods).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456211
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  • 8
    Electronic Resource
    Electronic Resource
    HOD spectroscopy and photodissociation dynamics: selectivity in hydroxyl/hydroxyl-d bond breaking (1989)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 93 (1989), S. 1840-1851 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100342a030
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of the transition dipole in Raman scattering (1989)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 93 (1989), S. 7107-7119 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100357a019
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  • 10
    Electronic Resource
    Electronic Resource
    Spectroscopic characterization of repulsive potential energy surfaces: fluorescence spectrum of ozone (1982)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 86 (1982), S. 2564-2566 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100211a004
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