RESONANCE RAMAN INVESTIGATION OF TRANS-AZOBENZENE IN THE LOWEST ENERGY (1)A(U) EXCITED-STATE

The excitation profiles of several Raman bands of trans-azobenzene solution in carbon tetrachloride were measured in resonance with the first allowed electronic transition peaked around 320 nm. The experimental results were analysed by means of a multi-mode Franck-Condon model to obtain some excited state molecular parameters; such parameters were found to reproduce well the red side of the absorption band whereas some inconsistencies between experiment and calculation persist on the UV side. This has been tentatively explained as due to the contribution of a higher energy electronic state whose absorption band is peaked around 287 nm and which may slightly affect the parameters obtained.