VIBRATIONAL ENERGY TRANSFER IN PROPYNAL UNDER COLLISIONLESS $CONDITIONS^{*}$

$^{*}$Research carried out at Brookhaven National Laboratory under contract with the U.S. Department of Energy and supported by its Office of Basic Energy Sciences.Author Institution:Investigations of vibrational energy redistribution in the polyatomic, propynal - $H-C \equiv C-C^{O}_{\backslash_{H}}$ , will be discussed. Dye laser-induced, visible fluorescence following low-level vibrational excitation with a $CO_{2}$ 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