Advanced continuum approaches for treating time correlation functions. The role of solute shape and solvent structure

Parsons D;Vener MV;Basilevsky MV

1999-01-01

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Abstract

Time correlation functions describing the solvent relaxation around a molecule of coumarin-153 and a benzophenone anion in acetonitrile are calculated using dynamical continuum theories of solvation with an experimental dielectric function epsilon(omega) including the resonance absorption region of the solvent. Apart from the local model with a single molecular-shaped solute cavity of the solute studied previously, a new dynamic local model with a double molecular-shaped cavity and a dynamic nonlocal theory with a spherical cavity are presented, both of which introduce elements of solvent structure. It is shown that both local models, one- and two-cavity, exhibit experimentally unobserved oscillations in the shorter time region t < 1 ps, although the experimental asymptote for t > 1 ps for coumarin is obtained. The dynamics of the two-cavity model are not seen to differ from those of the one-cavity model. The nonlocal dynamic theory is shown to be able to suppress these oscillations, but the long-time asymptote differs markedly from that of the local theories. The nature of this asymptote is studied analytically.