EFFICIENCY OF PRODUCTION OF XE-2-ASTERISK AND KR-2-ASTERISK EXCIMER MOLECULES IN MICROWAVE-DISCHARGE PLASMAS

A numerical model is developed for a weakly ionized plasma of a high-p ower microwave discharge in xenon and krypton when the microwave field frequency is higher than or comparable with the electron energy relax ation rate. The applicability range of the model is discussed. The kin etic models of the processes involved are tested under conditions corr esponding to a plasma excited by a high-energy electron beam. The mode l can be used to qualitatively describe the experimental intensity pro files of spontaneous emission from a plasma of high-power microwave di scharge in xenon and krypton. The efficiency of production of excimer molecules and the amplification properties of the active medium are st udied theoretically with allowance for the skinning effect and depende nce of the microwave power absorption along a gas-filled tube on the p lasma parameters. It is shown that, for a relatively low plasma electr on density, the efficiency of spontaneous emission from excimer molecu les attains 65.3% in Xe and 50% in Kr at a pressure of 10 atm and an e xcitation power of 0.6 MW/cm(3) The small-signal gain coefficient incr eases with increasing electron density and, hence, excitation power. I n particular, at a pressure of p = 5 atm, the net small-signal gain co efficient increases by a factor of 1.5 in Xe and almost doubles in Kr as the excitation power increases from 3 to 7 MW/cm(3). However, this increase is insufficient to explain the narrowing of spectral lines ob served in experiments.