Franck–Condon effects in low-energy states of C 10H 8+ radical. : Ab initio MCSCF study of absorption and resonance Raman spectra

Abstract

The Franck–Condon (FC) effects in the low-energy states of the C 10H 8 + radical are investigated in terms of ab initio FORS (full optimized reaction space) and SDE (single and double excitations) MCSCF calculational scheme applied with Dunning's double-zeta (DZV) basis set. This scheme is used to determine the excitation energies, the transition dipole moments and displacement (Franck–Condon) parameters for the three low-energy dipole-allowed 1 2 A u (D 0)→ 1 2 B 3 g (D 2), 1 2 A u (D 0)→ 1 2 B 1 g (D 3) and 1 2 A u (D 0)→ 2 2 B 1 g (D 4) transitions. The results of FORS MCSCF computations are compared to the QCFF/PI+CI and ROHF/3-21G results reported most recently for the C 10H 8 + radical. The resonance Raman (RR) spectra available in the region corresponding to the lowest-energy dipole-allowed 1 2 A u (D 0)→ 1 2 B 3 g (D 2) transition are discussed in some detail in the non-empirical fashion.