Knowledge Bank

The techniques of cavity ring-down spectroscopy and laser induced fluorescence are combined to simultaneously record the direct absorption and fluorescence excitation spectra of tropolone (TrOH) 5-hydroxytropolone (5-HOTrOH), and several TrOH-$(H2O)$ clusters cooled in a supersonic free jet. The large number of passes through the jet result in LIF scans of comparable quality to those involving single pass excitation, while avoiding saturation effects. Single vibronic level fluorescence (SVLF) quantum yields are thereby recorded with excellent signal to noise. TrOH and its derivatives are capable of intramolecular H-atom tunneling, either in symmetric or asymmetric double minimum wells. The direct absorption spectrum is recorded up to $2000cm-1$ above the $S1$ origin where the fluorescence quantum yield is negligible. Kin TrOH, correlations between the SVLF quantum yields and the H-atom tunneling splitting are explored. The single water molecule in the TrOH-$H2O$ complex is seen to increase e the fluorescence quantum yield of TrOH by almost a factor of 5. For 5 HOTrOH, highly mode specific mixing between syn and anti isomeric wells permits study of mode specific effects on non-radiative processes.