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(3s2-3p4) 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.