Resonance Raman quantum yields for CS2 in solution: Dynamics of solvent-induced spectral broadening

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Abstract
Electronic absorption spectra, resonance Raman spectra and quantum yields, and total emission yields have been measured for the S3←S0 transition of CS2 in cyclohexane, pentane, acetonitrile, hexadecane, and perfluorohexane solvents. The solution‐phase absorption spectra are significantly broadened and redshifted relative to the vapor. The solution‐phase S3 state lifetimes inferred from the total emission yields are 0.6–1.0 ps, close to the vapor‐phase lifetime, while the resonance Raman quantum yields imply electronic dephasing times of 25–50 fs in solution. This rapid dephasing due to intermolecular (solvent–solute) interactions is sufficient to account for almost all of the increased electronic spectral breadth in solution. The data are analyzed quantitatively with the aid of a stochastic theory of line broadening that accounts for solvent memory effects, and evidence is found for non‐Markovian (nonexponential in time) electronic dephasing. Possible physical origins for the rapid electronic dephasing in solution are suggested, and the relevance of these results to other dynamical processes in liquids such as activated barrier crossing and electron transfer reactions is discussed.