2,2 '-bithiophene radical cation: An experimental and computational study

Electronic absorption and resonance Raman spectra of the radical cation of bithiophene are reported. The bithiophene radical cation was produced by ga mma-radiolysis in a glassy matrix at 77 K, and the Raman spectrum excited i n resonance with the two absorption bands at 425 and 590 nm. The electronic states relevant to the observed electronic transitions were identified and characterized by CASSCF calculations. The optical absorption and resonance Raman spectra were calculated by wave packet propagation methods using the ab initio calculated molecular parameters. The calculated spectra agree we ll with the experimental ones. The importance of carrying out full wave pac ket propagation calculations is underlined by the fact that in one case the simple Savin formula gave a completely wrong prediction of the resonance R aman spectrum.