INTRAMOLECULAR VIBRATIONAL REDISTRIBUTI0N AS SEEN IN TIME RESOLVED EMISSION FROM p-DIFLUOROBENZENE

Author Institution: Department of Chemistry Indiana, University Bloomington; Environmental Science Department General, Motors Research Laboratories Warren; Department of Chemistry Indiana, University BloomingtonTime resolved fluorescence spectra are being obtained from several vibrational levels in $S_{1}$ p-difluorobenzene using the technique of chemical $timing.^{1}$ In this method varying pressures of the efficient electronic state quencher oxygen are used to restrict the fluorescence lifetime of the molecule to as little as 10 ps. Spectra taken in the presence of sufficient pressures of oxygen show a reduction in the fraction of emission which is structureless, an indication of incomplete IVR. These spectra are interpreted using kinetic models grounded in the predictions of the intermediate and statistical limit cases of radiationless transition $theory.^{2,3}$ At present it has been found that the intermediate case kinetics best fit data for the $3^{1} 5^{1} (\epsilon_{vib} = 2069 cm^{-1})$ and $3^{1} 5^{1} 30^{1} (\epsilon_{vib} = 2191 cm^{-1})$ levels with IVR rates on the order of 1 ns and 50ps respectively. 1. R.A. Goveleskie, D.A. Dolson, C.S. Parmenter, J. Chem. Phys. 72, 5774 (1980). 2. F. Lahmani, A. Tramer, and C. Trie, J. Chem. Phys. 60, 4431 (1974). 3. K. Freed, A. Nitzan, J. Chem. Phys., 73, 4765 (1980)