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Thermodynamics and kinetics of optically pumped discharges

Summary form only given. The paper addresses the fundamental problems of energy transformation in nonequilibrium laser-excited plasmas. It is well known that a laser can be considered a heat engine. In particular, in molecular gas lasers excited by an electric discharge, the high-temperature electrons (i.e. the hot reservoir) excite the high quantum states of the molecules (the upper laser levels). Work is extracted front the system by the emission of coherent radiation the induced transitions between the upper and the lower laser levels, u/spl rarr/1. The rest of the energy is ultimately returned to the translational mode (i.e. the cold reservoir) in collisional relaxation of the lower laser levels. Typically, the electron temperature in such lasers is T/sub e//spl sim/1-2 eV, and the gas translational temperature is T/spl sim/100-300 K. The efficiency of such an engine is e=(E/sub u/-E/sub 1/)/E/sub u/, where E/sub u/ and E/sub 1/ are the energies of the upper and the lower laser levels, respectively, which can be shown to equal the reversible engine thermodynamic efficiency.