Solvent-solute interactions probed by picosecond transient Raman spectroscopy : band assignments and vibrational dynamics of S1 trans-4,4'-diphenylstilbene

We present the ground- and excited-state Raman spectra of trans-4,4'-diphenylstilbene (DPS). We analyze the spectra on the basis of comparison with the Raman spectra of the ground- and excited-state and anion radical spectra of trans-stilbene and biphenyl. The excited-state Raman spectra of DPS in methylene chloride and dioxane exhibit mode-specific, solvent-dependent dynamics. Specifically, the intensities of several vibrational modes associated with the biphenyl portion of DPS are solvent dependent. We attribute the change in intensity to a variation in the Franck-Condon overlap between S 1 and S n caused by differences in the planarity of the biphenyl portion of DPS in the two solvents