Resonance Raman spectra of deuterated cis-stilbene

Resonance Raman intensities of perdeuterated cis-stilbene were measured usi ng 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 coeffic ients showing that the corresponding modes v(7), v(8), v(9) v(10), v(11) an d v(15) of d(12)-cis-stilbene have all of the Raman activity. The S-1 equil ibrium geometry and vibrational force field for cis-stilbene were calculate d at the CIS/6-31G(d) level and the vibrational assignment for the parent c ompound 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. Ther efore, in their determination the gradients of the Sr state, potential ener gy surfaces calculated at the ground-state geometry were also used. Even in its simplest form this approach reproduces the experiment fairly reasonabl y. Copyright (C) 2001 John Wiley & Sons, Ltd.