Collisional energy transfer from energy levels quest;1900 cmminus;1, produced by IR multiphoton absorption, C3H2O(vgsim;1)+Mrarr;C3H2O(v=1)+Mdeg;, is observed on a single collision basis by monitoring changes in the vibrational level populations of propynal as reflected in the laser excitation spectrum. It is concluded that vibrationthinsp;rarr;thinsp;vibration processes account for these observations and occur only with collision partners for which near resonant pathways exist. Under even the most favorable conditions (Dgr;E=40 cmminus;1), neither vibrationthinsp;rarr;thinsp;translation pathways nor multiple quantum changes involving nondriven modes are observed when ngr;6is the pumped mode. Observations suggest that multiple quantum events involving the pumped mode occur, but comparison of rate constants from different levels is hindered at present by the identification of overtones in the visible spectroscopy.
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