Resonance Raman and theoretical investigation of the photodissociation dynamics of benzamide in S3 state.

Resonance Raman spectra were obtained for benzamide in methanol and acetonitrile solutions with excitation wavelengths in resonance with the S(3) state. These spectra indicate that the Franck-Condon region photodissociation dynamics have multidimensional character with the motions mainly along the benzene ring C[Double Bond]C stretch nu(9), the Ph-CO-NH(2) and ring benzene stretch nu(14), the CCH in plane bend nu(17), the Ph-CO-NH(2) stretch and NH(2) rock nu(19), the ring trigonal bend nu(23), and the ring deformation and Ph-CO-NH(2) stretch nu(29). A preliminary resonance Raman intensity analysis was done, and the results were compared to those previously reported for acetophenone to examine the substituent effect. Solvent effect on the short-time photodissociation dynamics of benzamide was also examined. A conical intersection point S(2)S(3) between S(3) and S(2) potential energy surfaces of benzamide was determined by using a complete active space self-consistent field theory computations. The structural differences and similarities between S(3)S(2) point and S(0) were examined, and the results were used to correlate to the Franck-Condon photodissociation dynamics of benzamide in S(3) state.