Symmetry-breaking effects on photoinduced processes in solution

Raman and resonance Raman spectroscopies are employed to explore the degree of solvent-induced symmetry breaking int he ground and excited electronic states of the nominally symmetric linear molecules CS2 and I3-. A signature of broken symmetry is intensity in the antisymmetric stretching fundamental. CS2 breaks symmetry only slightly in all solvents examined, and the effects on the nuclear dynamics of the S3 excited state appear to be minimal. In I3-, 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 photodissociated process indicate a significant influence of asymmetry of the reactant on the dynamics of product formation.