Population of the lower active level in a carbon dioxide laser

Measurements were made of the temperatures of the deformation vibrations of the CO₂ molecules by the method of reversal of spectral lines in the 15 μ region. A comparison of the vibrational temperatures obtained in this way with the calculated temperatures of the gas indicated that the population of the lower laser level was in equilibrium. Parallel measurements of the temperature of the antisymmetric vibrations of the CO₂ molecules made it possible to determine the absolute populations of the laser levels and the population inversion. A comparison was made with the results obtained by the method of amplification of a laser signal.