Resonance Raman study of Franck-Condon effects in the C10H8+ radical. Ab initio MCSCF calculations for the low-energy 2B2g and 2B3g symmetry states

Resonance Raman spectra in the region corresponding to the 2Au(Do) → 1 2B3g(D2) electronic excitation of the naphthalene cation (C10H8+) are studied in terms of a model based on Franck-Condon (FC) effects. This simple model correctly accounts for the RRS spectra and yields FC parameters which correspond to those obtained from ab initio MCSCF computations. Computed FC activities of nine totally symmetric modes in the 2B3g(D2) and 2B2g(D4) states of the C10H8+ radical are discussed and compared to experiment and earlier theoretical based studies on the ROHF/3-21G approach.