βResearch 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 - HβCβ‘CβC\HβOβ , will be discussed. Dye laser-induced, visible fluorescence following low-level vibrational excitation with a CO2β laser is used to monitor the internal energy distribution under collisionless conditions (10β5 to 10β3 torr). Time resolved spectroscopic changes in Ξ½6β (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 ΞΌsβ. 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