A picosecond time-resolved resonance Raman study of S1 cis-stilbene

The time-resolved resonance Raman (TR3) spectrum of S1 cis-stilbene inn-hexane is presented. Raman bands are observed at 243, 475, 742, 977, 1200 and 1440 cm−1. Their positions and relative intensities suggest that these belong to a high-order overtone progression (up to the fifth order) originating from the 243 cm−1 fundamental. This observation implies a large difference between S1 and the resonantSn states in the equilibrium nuclear coordinate corresponding to the 243 cm−1 mode, with displacement Δ ∼ 12. Ground and excited state equilibrium geometries and frequencies are determined using ab initio molecular orbital calculations.