Symmetry-breaking effects on photoinduced processes in solution

Raman and resonance Raman spectroscopies are employed to explore the degree of solvent-induced symmetry breaking in the ground and excited electronic states of the nominally symmetric linear molecules CS2 and I-3-. A signature of broken symmetry is intensity in the antisymmetric stretching fundamental, v(3). CS2 breaks symmetry only slightly in all solvents examined, and the effects on the nuclear dynamics of the S-3 excited state appear to be minimal. In I-3-, asymmetry is pronounced in alcoholic solvents but undetectable in acetonitrile. MCSCF/RISM calculations support the experimental result and indicate that solvent stabilization of separated charges renders a wide range of asymmetric ground-state structures energetically accessible. Recent femtosecond time-domain studies of the photodissociation process indicate a significant influence of asymmetry of the reactant on the dynamics of product formation.