Influence of small oxygen additions on the small-signal-gain dynamics in the active medium of a pulsed electron-beam-controlled discharge CO laser

The method for measuring the rate constants of the VV' exchange between CO and O-2 molecules is developed. The method is based on a comparison of the measured and numerically calculated small-signal-gain (SSG) dynamics in the active medium of a pulsed electron-beam-controlled cryogenic CO laser. The SSG dynamics was measured in CO-He-O-2 mixtures with the fixed CO:He = 1:4 ratio by varying the oxygen content from 0 to 4%. The SSG dynamics was measured by probing the active medium of the pulsed CO laser by a beam from a tunable cw CO laser. The mathematical model of the CO laser takes into account the influence of oxygen on energy exchange processes. The parameters of the analytic approximation for constants of the near-resonance VV' exchange CO (upsilon) + O-2 (u = 0) -> CO(upsilon - 1) + O-2 (u = 1) are determined by the developed method for quantum vibrational numbers upsilon = 18 - 24. In particular, the rate constant for upsilon = 20 is (3.1 +/- 0.5) x 10(-12) cm(3) s(-1) at the gas temperature of 150 K. The extrapolation of the obtained analytic expression for rate constants in gases at room temperature gives the reasonable agreement with the measurements performed earlier for upsilon = 12 and 13.