Measurement of vibrational–vibrational energy transfer probabilities in CO–CO collisions by a fast flow approximation

The vibrational–vibrational (V–V) energy transfer probability P0,1v,v−1 in CO–CO collisions, CO(0)+CO(v) → CO(1) + CO(v−1), has been measured from the first overtone emission spectra for v=3 to v=9 from vibrationally excited CO* produced in the reaction of oxygen with acetylene at room temperature. Under fast flow conditions in which spontaneous radiative rates, collisional deactivation rates, and other loss rates are made much smaller than the volumetric pumping rate, we find that the solution of the master equations for the vibrational population can be simplified and V–V transfer rates can be accurately determined. We call this approach the ’’fast flow approximation.’’ The experimental results are compared with previous work and with a calculation that includes both long-range and short-range interaction potentials.