Electron-Energy-Loss Spectroscopy of Spin-Forbidden Transitions with Vibronic Resolution: The Lowest Triplet State of Fluorobenzenes

摘要

Low-energy electron-energy-loss spectra in the range of the lowest triplet state are presented for solid benzene, fluorobenzene, and p-difluorobenzene deposited at a temperature of 30 K. Vibronic structure within the triplet ands of fluorobenzene and p-difluorobenzene is observed for the first time. The spectrum of fluorobenzene closely resembles that of benzene, whereas p-difluorobenzene shows characteristic differences. The spectra of all three molecules are dominated by pure progressions of the totally symmetric ring-breathing vibrational mode v_1.