The Attenuation of 3.392 He-Ne Laser Radiation by Methane in the Atmosphere
01 February 1966
The proximity of the 3.392^ He-Ne laser emission to one of the absorption lines of methane 1,2 predicts that this laser radiation may be somewhat attenuated by the earth's atmosphere. The characteristics of this attenuation are interesting not only in evaluating the potential use of the 3.392/u. line for communications, but also because of possible application in measurement of the methane content in the atmosphere. An estimate of the absorption of 3.392/x laser emission by methane in the atmosphere has appeared in the literature. 1 The purpose here is to present a measurement which compares propagation of infrared waves at 3 . 3 9 2 a n d 3.508/x over an atmospheric path length of 2.6 km. The differential transmittance at these two wavelengths, after accounting for the effect of water vapor, is used to determine the attenuation of the 3.392^ wave by methane in the atmosphere.