Optogalvanic Effect Study of Vibrational Relaxation in CO2Laser Process

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Abstract
The amplitude and phase retardation of the optogalvanic signal in a CO2–N2–He laser plasma irradiated by a 10.6 µm CO2laser were measured under various experimental conditions. It is shown that the mechanism of the optogalvanic effect is related to the vibrational relaxation processes of the laser levels. The collisional rate constant relevant to the upper laser level (001) is determined as (2.6±0.5)×102/Torr·s at 300 K. Good agreement is obtained between the present value and the value previously obtained by the infrared pulse gain method. A new model for the optogalvanic effect is proposed, taking three relaxation processes into consideration. The dependence of the optogalvanic effect on the pressure and modulation frequency is calculated using this model and a reasonable set of parameters, and shows good agreement with the observations.