The Jahn-Teller effect in the lower electronic states of benzene cation. II. Vibrational analysis and coupling constants of the B~2E_(2g) state

摘要

The vibrational structure seen in photinduced Rydberg ionization spectra of the B ~2E_(2g) state of benzene cation (C_6H_6~+ and C_6D_6~+) has been analyzed by fitting the vibrational patterns to energy levels derived from multimode Jahn-Teller calculations. Most of the structure can be ascribed to various combinations of modes 6 and 16, with minor contributions from 4, 17, and 18 (using Wilson's numbering convention). In qualitative agreement with parameters derived from electronic structure calculations, the linear coupling parameter for mode 6 is very large (D = 1.39 in C_6H_6~+ and 1.28 in C_6D_6~+). This raises questions about certain angular momentum selection rules in the classical Jahn-Teller model.