Spectroscopic and dynamical studies of vibrationally unrelaxed fluorescence from halobenzene cations in a neon matrix

By use of selective temporal detection, it has been possible to detect vibrationally unrelaxed emission from several different halobenzene cations in a Ne matrix. The observation of such unrelaxed emission allows detailed information to be obtained about the ground-state vibronic structure of the ions, since optical selection rules prohibit transitions between many of these levels and the excited-state vibrationless level. By comparing relative intensities of relaxed and unrelaxed emissions, one can obtain a measurement of the lifetimes of the excited electronic state's vibrationally excited levels.