Chemiluminescence from the supersonic jet of a cw HF chemical laser

The spontaneous emission from HF infrared bands in the free jet of a continuous HF chemical laser with a slit nozzle bank has been measured at a number of downstream positions. Three flows are reported: He–SF6–H2-(1) with O2, (2) without O2, and (3) with reduced SF6 without O2. Spatially averaged number densities of the HF vibrational levels (ν = 1, 2, 3, 4) have been determined during zero-power conditions. Vibrational nonequilibrium is evident. The largest HF densities are ∼1015 No./cm3. Observed rotational temperatures, equilibrated to jet static temperature, range from 560 down to 390°K. The largest zero-power gain coefficient deduced is 0.12 cm−1 on the P branch of the 2 → 1 band.