WAVEPACKET DYNAMICAL STUDIES ON TRANS-AZOBENZENE - ABSORPTION-SPECTRUM AND RESONANCE RAMAN EXCITATION PROFILES OF THE N-PI-ASTERISK TRANSITION

Time-dependent wavepacket propagation techniques have been used to cal culate the absorption spectrum and the resonance Raman excitation prof iles of the n-pi transition in azobenzene. A comparison of both the c alculated absorption spectrum and excitation profiles with experiment has been made. From an analysis of the data, it is concluded that the Raman intensities are mainly due to resonance from the n-pi transitio n and not from the pre-resonance of the pi-pi transition, as reported earlier. We find that the isomerization pathway is through the invers ion mechanism rather than by rotation. This is the first direct spectr oscopic evidence for the isomerization pathway in trans-azobenzene.