SINGLE VIBRONIC LEVEL FLUORESCENCE-SPECTRA FROM (A)OVER-TILDE(B-1(2U)) BENZENE - FERMI RESONANCES AND S-0 IVR LIFETIMES

We report measurements of single vibronic level fluorescence spectra o f benzene cooled in a supersonic expansion. The levels for which spect ra have been recorded are 0(0), 1(1), 6(1), 6(1)1(1), 6(1)1(2), and 6( 1)1(3). The spectra reveal Fermi resonances in both the excited and gr ound electronic states. The analysis of these resonances is reported, in particular the 6(1)1(1)-8(1) resonance which permeates the spectra. From the analysis some ground state anharmonicity constants involving nu(8) have been determined. High resolution scans of the transitions provide upper bounds to the rates for intramolecular vibrational energ y redistribution (IVR) from S-0 levels up to similar to 9200 cm(-1).