Effect of H2 Pressure on Pulsed H2+F2 Laser. Experiment and Theory

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Abstract
Stimulated emission predictions and measurements for an H2+F2 laser are compared for H2 pressures from threshold to stoichiometric, a range of several orders of magnitude. Slowly flowing, helium‐diluted, 50 torr mixtures are initiated photolytically. Two dilution ratios and two output couplers are considered, and good agreement is found for time‐to‐threshold and pulse duration vs H2 pressure. Spiking, relaxation oscillations, and possibly mode beating, features not modeled, are observable in some pulses; however, predicted intensity vs time generally agrees in pulse shape with laser output. Observed and predicted peak intensities nearly match for low H2 pressure, and the predicted increase of peak intensity with low H2 is followed fairly well. For H2 in the vicinity of one‐tenth stoichiometric, the peak intensity data show an abrupt leveling off, while the calculations predict a continuing increase. This disagreement most probably cannot be attributed to uncertainties in the kinetic model. All rate modifications considered have proven incapable of producing a change sufficiently large or abrupt to explain this feature of the data. Experimental results are presented supporting the notion that parasitic oscillations cause this change in laser output.