He-Ne laser frequencies near 2.4 microns and their application to hydrogen fluoride detection

Eberhardt and Pryor (1982) have reported that emission near 2.40 microns from an He-Ne laser coincides very closely with the 1R(5) absorption frequency of hydrogen fluoride and may, therefore, be used to monitor the presence of HF in the atmosphere. The mismatch between the center frequency of the laser line and that of the 1R(5) HF absorption line appears to be on the order of 100 MHz and, therefore, is negligible when the HF line is broadened to a width of approximately 1000 MHz in the atmosphere. The absorption cross section (2.0 x 10 to the -18th sq cm/HF molecule in the atmosphere) is sufficient to detect HF at a level of approximately 20 microgram/cu m in a 500 m atmospheric path. It is found that three frequencies near 2.4 microns can be conveniently obtained from an He-Ne laser.