SCALED AB-INITIO FORCE-FIELD OF E- AND Z-HEXATRIENE IN THE S-0 AND T-1 STATES

The structures of the S-0 and T-1 states of E- and Z-hexatriene are op timized at several levels of ab initio theory. The corresponding force fields and harmonic frequencies are calculated for a number of isotop omers in both states. Excellent agreement between theory and experimen t is obtained by applying the scaling parameters for So to the T, forc e field. The time-resolved resonance Raman data available for the trip let state of E- and Z-hexatriene are reviewed in the light of the pres ent ab initio results and the spectra are found to be due only to the E isotopomers.