A Study of Raman Excitation Profiles for Soluble cis-Polyacetylene

Abstract

A quantitative analysis of the Raman excitation profiles (REPs) for soluble cis-polyacetylene, cis-(CH)_x, in toluene observed by Sassi et al. was undertaken. This analysis took two approaches, namely improved vibronic interaction theory and resonance-Raman scattering theory for solute molecules coupled homogeneously and strongly to a continuum of environmental nuclear modes. For the former theory, a ‘static’ approach, the effect of inhomogeneous environmental broadening of REPs of a solute molecule due to the solvent–molecule interactions was investigated as well as the role of diagonal and non-diagonal terms of the scattering matrix. For the latter theory, a ‘dynamic’ approach which rests on vibrational density matrices including both molecular and solvent modes in the ground and excited electronic states, the solvent effects are regarded as dynamic and homogeneous. The values of the equilibrium coordinate shifts for the Raman-active mode and the homogeneous and inhomogeneous broadening parameters derived from the REPs by both approaches are compared with theoretical results of previous studies of soluble and of solid cis- and trans-(CH)_x.