Picosecond solvation dynamics of S1 t r a n s-stilbene by nanosecond transient Raman spectroscopy with ‘‘optical depletion timing’’

The laser-power dependent Raman spectral changes observed for S1 trans-stilbene in hexane are analyzed in terms of the competition between a picosecond solvation process occurring immediately after the S1←S0 photoexcitation (by the pump laser) and the optical depletion of the S1 state caused by the Sn←S1 photoexcitation (by the probe laser). Such spectral changes were not observed in acetonitrile, indicating that the solvation process is absent in a polar solvent. The scheme of ‘‘optical depletion timing’’ is demonstrated to be useful as an effective means to study picosecond phenomena by nanosecond spectroscopic measurements.