PHOTOINDUCED RYDBERG IONIZATION (PIRI) SPECTROSCOPY OF THE B STATE OF THE FLUOROBENZENE CATION

Vibrationally resolved PIRI spectra of the B state of the fluorobenzene cation via the origin, 16a, 6b, and 11 vibrational modes in the ground ionic state require a reassignment of the accepted state symmetry. On the basis of lower resolution studies, the B ← X transition has been previously assigned as an electronically forbidden 2B2 ← 2B1 transition. Vibrational analyses of the spectra observed via various ground-state nonsymmetric vibrations, particularly from the 16a vibrational mode, unambiguously locate the origin of the transition at 21 075 cm-1, resulting in the reassignment of the ionic state as 2B1. Ab initio calculations, while not conclusive, also suggest that the B ← X transition is an allowed π to π transition.