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 S3 state. These spectra indicate that the Franck–Condon region photodissociation dynamics have multidimensional character with the motions mainly along the benzene ring C==C stretch ν9, the Ph–CO–NH2 and ring benzene stretch ν14, the CCH in plane bend ν17, the Ph–CO–NH2 stretch and NH2 rock ν19, the ring trigonal bend ν23, and the ring deformation and Ph–CO–NH2 stretch ν29. 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 S2/S3 between S3 and S2 potential energy surfaces of benzamide was determined by using a complete active space self-consistent field theory computations. The structural differences and similarities between S3/S2 point and S0 were examined, and the results were used to correlate to the Franck–Condon photodissociation dynamics of benzamide in S3 state. [ABSTRACT FROM AUTHOR]