FRANCK-CONDON EFFECTS IN LOW-ENERGY STATES OF C10H8- AB-INITIO MCSCF STUDY OF ABSORPTION AND RESONANCE RAMAN-SPECTRA( RADICAL )

The Franck-Condon (FC) effects in the low-energy states of the C10H8radical are investigated in terms of ab initio FORS (full optimized re action space) and SDE (single and double excitations) MCSCF calculatio nal scheme applied with Dunning's double-zeta (DZV) basis set. This sc heme is used to determine the excitation energies, the transition dipo le moments and displacement (Franck-Condon) parameters for the three l ow-energy dipole-allowed 1 (2)A(u)(D-0) --> 1 B-2(3g)(D-2), 1 (2)A(u)( D-0) --> 1 B-2(1g)(D-3) and 1 (2)A(u)(D-0) --> 2 B-2(1g)(D-4) transiti ons. The results of FORS MCSCF computations are compared to the QCFF/P I + CI and ROHF/3-21G results reported most recently for the C10H8+ ra dical. The resonance Raman (RR) spectra available in the region corres ponding to the lowest-energy dipole-allowed 1 (2)A(u)(D-0) --> 1 B-2(3 g)(D-2) transition are discussed in some detail in the non-empirical f ashion. (C) 1998 Elsevier Science B.V. All rights reserved.