VIBRATIONAL RELAXATION OF ELECTRONICALLY EXCITED MOLECULES IN THE VAPOUR PHASE

Abstract

The relaxation of vibrational energy of some aromatic hydrocarbons in the gas phase has been measured by using time-resolved fluorescence spectroscopy on a nanosecond time scale. Relaxation efficiencies have been obtained for various inert gases. The energy dependence of lifetimes and relative quantum yields of $S_{1}$- and $S_{2}$-fluorescence, measured under collision-free conditions, provides a calibration method for the energy content of the aromatic molecule during the relaxation process. Detailed information about the relaxation processes in glyoxal is obtained from time-resolved fluorescence decay measurements in the low pressure vapour. Recent experimental results will be presented.