An MCSCF study of the X 2 B 2, 2 A 2 and 2 2 B 2 states of benzyl

A large basis set (double-zeta + polarisation and diffuse s, p on carbons) calculation is reported on the three electronic states of benzyl, X2B2, 2A2 and 2 2B2, which are of interest experimentally. Because these states cannot be represented by SCF wavefunctions, CASSCF π-space calculations are performed. Geometries are optimised. It is found that the X2B2 state is 65 kcal mol–1 lower than the 2 2B2 and 2A2 states, which these calculations suggest have nearly the same energy (within 2 kcal mol–1). These results agree with the most recent interpretation of emission and absorption spectra.