Knowledge Bank

Investigations of vibrational energy redistribution in the polyatomic, propynal - $H-C\equiv C-C\setminus HO$ , will be discussed. Dye laser-induced, visible fluorescence following low-level vibrational excitation with a $CO2$ laser is used to monitor the internal energy distribution under collisionless conditions ($10-5$ to $10-3$ torr). Time resolved spectroscopic changes in $\nu 6$ (C-C Stretch), the pumped mode, show that increases in population in the v=1 level follow closely the shape of the excitation pulse and that decay is exponential to 10 $\mu s$. However, concomitant changes in hot bands of other modes, especially those of lower frequency, are not obvious. These results will be discussed in terms of intramolecular, V-V, and V-T energy transfer.