Investigation of weak absorption lines of gases with a laser spectrophone

The results are given of an experimental investigation of the dependence of the absorption coefficient of atmospheric water vapor (λ=694.38 nm) on the power of resonant radiation of a ruby laser. The measurements were carried out using a laser spectrophone, which is an instrument based on the opticoacoustic detector. A description is given of a method for the calibration of the spectrophone, which makes it possible to find the absolute values of the absorption coefficient. It is reported that the absorption of water vapor reaches saturation when the power density of the laser radiation is increased from 30 to 400 MW/cm². A possible origin of the observed saturation is suggested.