The chain reaction between hydrogen and fluorine mixed with helium has been successfully employed to generate laser emission from HF. Chemical reaction was initiated by flash photolysis of the reagents premixed at room temperature. Evidence for participation of the ``hot'' reaction,Hmiddot;plus;F2rarr;HF*plus;Fmiddot;, in the laser pumping mechanism is presented. Approximately 7percnt; of the laser radiation from this system is at wavelengths longer than 3.04 mgr; indicating that the large exothermicity of the ``hot'' reaction is not temporarily stored as population inversion between high vibrational levels of newly formed HF. Power and energy outputs up to 18 W/cc and 0.5 mJ/cc have been measured from dilute mixtures (40:1) at total pressures of 130 torr. Smallhyphen;signal gains of 3percnt;/cm, chemical efficiencies ofsim;1percnt;, and pulses having durations up to 140 mgr;sec were observed. Computer calculations of reaction times are in good agreement with the pulse durations observed for a variety of experimental conditions.
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