Articles you may be interested in K selection in one-photon mass-analyzed threshold ionization of C H 3 I and C D 3 I to the X ̃ E 3 ∕ 2 2 state cations J. Chem. Phys. 128, 044310 (2008); 10.1063/1.2823032 Diradicals, antiaromaticity, and the pseudo-Jahn-Teller effect: Electronic and rovibronic structures of the cyclopentadienyl cationThe Jahn-Teller effect in the lower electronic states of benzene cation. II. Vibrational analysis and coupling constants of the B̃ 2 E 2g state Photoinduced Rydberg ionization ͑PIRI͒ spectroscopy has been applied to the problem of recording vibrationally resolved spectra of the dipole-forbidden B 2 E 2g ←X 2 E 1g transition of C 6 H 6 ϩ and C 6 D 6 ϩ . 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, 16 and 17 , 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.

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A new method for the high-resolution electronic spectroscopy of cations with mass resolution. Optical transitions from Rydberg states converging on the ground state of the cation to states with electronically excited cores are detected by their rapid autoionization. The spectrum of these transitions provide ionic information because the photoabsorption cross-section of a molecule in a high-n Rydberg state closely mirrors the spectrum of the ion core. The technique presented here, called photoinduced Rydberg ionization (PIRI) spectroscopy, is applied in this case to record the B̃ 2E2g→X̃ 2E1g transition of the benzene cation via the vibrational origin of the X̃ 2E1g ionic state.