Structure of C6HF+ and C6F2+ fragment ions from fluorobenzenes : electronic spectra in 6 K neon matrices

The fragment ions C6HF+ and C6F2+ produced from fluorobenzenes in a discharge source were trapped in 6 K neon matrices after mass selection. A strong absorption system is detected in the visible range starting at 586.3 nm for C6HF+ and 569.3 nm for C6F2+. Vibrationally resolved fluorescence commencing at the same wavelengths is observed upon laser excitation into each absorption band of these cations. The absorptions are assigned to the A2Πg ← X2Πu and A2Π ← X2Π transitions of linear FC6F+ and HC6F+, respectively. The assignment is based on the similarity of the absorption and fluorescence spectra with the A2Πg ← X2Πu electronic system of linear HC6H+ as well as the theoretically calculated vibrational and electronic excitation energies of the FC6F+ and HC6F+.