Resonance Raman spectra of deuterated cis‐stilbene

Abstract

AbstractResonance Raman intensities of perdeuterated cis‐stilbene were measured using excitation at 266 nm. For the six analysed bands at 1612, 1564, 1537, 1372, 1325 and 958 cm−1, no large changes in intensity distribution relative to the parent compound were found in accordance with the scrambling coefficients showing that the corresponding modes ν7, ν8, ν9, ν10, ν11 and ν15 of d12‐cis‐stilbene have all of the Raman activity. The S1 equilibrium geometry and vibrational force field for cis‐stilbene were calculated at the CIS/6–31G(d) level and the vibrational assignment for the parent compound and some of its symmetrically substituted isotopomers is considered. The obtained excited‐state geometry distortions are large, preventing the use of a simple displacement equation for relative Raman intensities. Therefore, in their determination the gradients of the S1 state, potential energy surfaces calculated at the ground‐state geometry were also used. Even in its simplest form this approach reproduces the experiment fairly reasonably. Copyright © 2001 John Wiley & Sons, Ltd.