Investigation of the dynamics of formation of excited atoms, ions, and excimer molecules in the plasma of an electric-discharge XeCl laser

The plasma of an electric-discharge XeCl laser was investigated by the method of absorption probing with tunable dye laser pulses. The duration of a probe pulse was 7 nsec and the half-width of the laser line was 15 pm. A synchronization system made it possible to shift the probe pulse on the time scale relative to the discharge and this could be done with an accuracy of 3 nsec. The absorption spectra were determined in the range 335–610 nm for a mixture of the composition He:Xe:HCl = 550:8:1 at a pressure of p = 2.2 atm. The time dependences of the absolute concentrations of Xe*, He*, Xe⁺*, and Cl^– were obtained. The dynamics of population of excited atoms and ions was analyzed. Amplification of a small signal was used to determine the time dependence of the absolute concentration of XeCl* excimer molecules. It was found that during the initial stage of the discharge the dominant XeCl* formation channel was a harpoon reaction, whereas during later stages the ion–ion recombination process predominated.