THE 21A1 STATE OF CIS-HEXATRIENE VAPOR - RESONANCE RAMAN-SPECTRA

Raman spectra have been obtained on resonance with the 2 1A1 state of room temperature cis-1,3,5-hexatriene vapor at 290.8 nm. Overtones and combination bands of totally symmetric stretching and bending modes, both alone and in combination with an interval probably assignable as the overtone of the lowest frequency skeletal bending mode of b1 symmetry, are strongly enhanced. Vibrational intervals tentatively assigned to the a2 and b2 methylene torsions are also observed, consistent with a large change in the force constant for =CH2 twisting in the 2 1A1 state.