Fluorescence spectrum of the benzyl radical in methylcyclohexane at 4.2 K

The fluorescence spectrum of the benzyl radical (BR) is characterized by participation of many totally symmetric vibrational modes with less intensity activeness. To make this point more clear, the fluorescence spectra of the benzyl radical and its deuterated compounds in methylcyclohexane (MCH) have been observed at 4.2 K and detailed vibrational analysis has been carried out. Two non-totally symmetric modes such as nu6b and nu8b play a role of Herzberg-Teller type vibronic coupling together with one totally symmetric mode nu6a. There are only a few progression bands with very weak intensity. These are nu12, nu1 and nu(phi-CH2) vibrational modes.