LIFETIME AND QUENCHING OF CO ($a^{3}\Pi$) IN A FLOWING HELIUM AFTERGLOW
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Date
1971
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Ohio State University
Abstract
Spectroscopic observations from 190 to 800 nm of a fast-flowing helium afterglow have shown CO (a $^{3}\Pi$) is a major product of the reaction of He (2 $^{3}$S) metastable atoms with carbon dioxide. Studies carried out in a helium bath at pressures near 1 torr have proved convenient for observing the long lived triplet of CO by means of the emission between 190 and 260 nm of the Cameron Bands, the a $^{3}\Pi$ --- X $^{1}\Sigma$ system. Measurements of the decay of the CO a $^{3}\Pi$ emission as a function of distance in the flowing helium have been used to measure the radiative lifetime of the a $^{3}\Pi$ state and the quenching of this state by $CO_{2}$ and by helium. Rates of removal of the CO (a $^{3}\Pi$) by $CO_{2}$ and He at room temperature over the pressure range from 0.1 to 3 torr have been measured as $(1.6 \pm 0.3) \times 10^{-11}$ $cm^{3}$ $sec^{-1}$ and $(6 \pm 3) \times 10^{-14}$ $cm^{3}$ $sec^{-1}$, respectively. The radiative lifetime was found to be between 2.5 and 20 msec.
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This research was supported, in part, by NASA, Grant No. NGR 05-010-044.""
Author Institution: Department of Physics, University of California
Author Institution: Department of Physics, University of California