RESONANCE RAMAN-SPECTRA AND EXCITATION PROFILES OF (Z)-1,3,5-HEXATRIENE VAPOR

UV resonance and preresonance Raman spectra of (Z)-1,3,5-hexatriene vapor in resonance with the 1 1A1 --> 1 B-1(1) transition, using 11 excitation wavelengths in the region 262-232 nm, are reported. The resulting excitation spectra for the observed fundamental vibrational modes, overtones, and combinations are presented. The spectra are interpreted on the basis of theoretical calculations using the time-dependent wave-packet propagation formalism. A best fit for the absorption spectrum and resonance Raman excitation profiles is calculated by parametrizing a model for the excited-state potential energy surface. Temperature effects and Duschinsky mixing are included in the model. The potential energy surface of the 1 B-1(1) excited singlet state is found to have a local minimum at the planar Z geometry.