The observation of strong pseudo-Jahn–Teller activity in the benzene cation B 2E2g state

Goode, Jon G.; Hofstein, Jason D.; Johnson, Philip M.
August 1997
Journal of Chemical Physics;8/8/1997, Vol. 107 Issue 6, p1703
Academic Journal
Photoinduced Rydberg ionization (PIRI) spectroscopy has been applied to the problem of recording vibrationally resolved spectra of the dipole-forbidden B 2E2g←X 2E1g transition of C6H6+ and C6D6+. PIRI spectra of the B state have been recorded via a number of vibrational states of the ionic ground state. A combination of Herzberg–Teller and pseudo-Jahn–Teller vibronic coupling between the B state and a close lying C state were used to explain the complex B state vibrational structure. The two pseudo-Jahn–Teller vibrational modes, ν16 and ν17, were both found to be active in the PIRI spectra. In addition, evidence for a strong pseudo-Jahn–Teller interaction within each of these modes was found. The perturbed vibronic bands resulting from this pseudo-Jahn–Teller activity were successfully modeled using a two-mode pseudo-Jahn–Teller vibronic coupling model. Using a combination of the spectral results and the pseudo-Jahn–Teller calculations, we were able to generate absolute vibronic symmetry assignments for many of the lower B state vibrational levels, from which vibrational assignments were made. The calculations also produced unperturbed vibrational frequencies for both pseudo-Jahn–Teller active modes along with values for their respective linear coupling constants. © 1997 American Institute of Physics.


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