Switching of the emission wavelength of a helium-neon laser in the 3.39 μ region

The emission switched from the λ = 3.3922 μ 5s' [1/2]⁰₁ – 4p' [3/2]₂ (3s₂ – 3p₄) line to the λ₁ = 3.3912 μ 5s' [1/2]⁰₁ – 4p' [1/2]₁ (3s₂ – 3p₂) line in such a way as to maximize the power at the λ₁ wavelength. The absorption of both lines was determined in pure methane in the pressure range 0.05–1 atm and in methane-air mixtures at atmospheric pressure; a comparison was made of the gains of these lines in a helium-neon discharge.