THE T-1 RESONANCE RAMAN-SPECTRA OF BIOCHEMICALLY RELEVANT CHROMOPHORES - A THEORETICAL INVESTIGATION

The vibrational structure of the T-1 resonance Raman spectra of hexatr iene, beta-ionylidene acetaldehyde (C15 aldehyde) and beta-carotene ar e analyzed with the help of semiempirical and ab initio quantum chemic al calculations. The T-1 equilibrium structures and vibrational force fields of the mono-cis- and trans-isomeric species are obtained and em ployed to model the spectra under the assumption of a dominant Franck- Condon mechanism. The simulations are used to identify the species tha t contribute to the observed spectra and to map the shape of the T-1 p otential energy surface. (C) 1997 Elsevier Science S.A.