The temporal properties of the number density of nitrogen atoms were studied during the decay period of plasmas produced in nitrogen by measuring the intensity of the first positive bands during this period. From the analysis of these data the value of the surface catalytic efficiency γ of a sputtered molybdenum layer on quartz and Pyrex for the recombination of nitrogen atoms was determined for gas pressures varying from 0.1 to 5 Torr and gas temperatures in the range 85–500 °K. A theoretical model explaining the data was derived.
The time dependence of the intensity of various emission bands during the decay period of plasmas produced in pure nitrogen was measured using the stationary afterglow method. Two processes involving the N2 (A3Σu+) metastable molecule were found to populate the N2 (B 3Πg) state during the nitrogen afterglow. The first process is the energy pooling reaction N2 (A3Σu+)+ N2 (A3Σu+) → N2 (B3Πg)+N2 (X1Σg+), which also populates the N2 (C 3Πu) and N2 (C′3Πu) states. An approximate value for the reaction rate constant for this process was found to be (1.1−0.5+2)× 10−9 cm3 sec−1 per molecule. Strong evidence was found that N2 (B 3Πg) is also populated by the reaction N2 (A3Σu+)+N2* (X)→N2 (A3Σu+, v′>7)+N2(X)→ N2 (B3Πg)+N2 (X), where N2* (X) is a vibrationally excited ground state nitrogen molecule. The population of the N2 (B 3Πg) energy state by recombination of nitrogen atoms was also observed.
The intrinsic power efficiency of the atomic xenon laser depends upon the electron density because of the mixing of the laser levels by electron collisions while the electron density in high-pressure particle-beam excited plasmas increases with increasing gas temperature. Therefore, in order to reduce the amount of electron collisional mixing when operating at high-energy loadings (> 100's J/l-atm) mixtures having a high-heat capacity are required. In particle-beam excited Ar/Xe mixtures, which typically yield the highest intrinsic laser efficiencies, increasing the gas pressure to increase the heat capacity is not always practical due to the high-stopping power of the gas mixture. For this reason we have experimentally and theoretically investigated adding He to Ar/Xe mixtures in studies of a fission-fragment excited atomic xenon laser. Adding He increases the heat capacity without appreciably perturbing the favorable kinetics resulting in efficient operation of the laser in Ar/Xe mixtures. We find that when adding He to Ar/Xe mixtures the dominant laser transition switches from 1.73 to 2.03 pm without significantly decreasing the efficiency. The laser pulse length also increases, an effect attributed to a lowering of both the electron temperature and gas temperatures.
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