Interferometric measurements of the atmospheric absorption of iodine laser radiation

Interferometric measurements were made of the absorption of iodine laser radiation in air. It was found experimentally that the main contribution to the absorption comes from water vapor. The dependence of the absorption cross section for water molecules at λ = 1.315 μm on the air pressure was determined. Its value at atmospheric pressure was found to be (6.8 + 0.8) X 10^– 25 cm². The absorption coefficient measured in dry air was (8.0 + 3.5) X 10^– 8 cm^– 1. The results were compared with calculations. A holographic method developed for analyzing the interferograms made it possible to measure interference fringe shifts of 1/100 of the fringe width or less and to observe the temporal and spatial evolution of a phase inhomogeneity.