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

The emission switched from the lambda$sub 0$=3.3922 $mu$ 5s'1/2$sup 0$$sub 1$--4p' 3/2$sub 2$(3s$sub 2$--3p$sub 4$) line to the lambda$sub 1$=3.3912 $mu$ 5s'1/2$sup 0$$sub 1$--4p'1/2$sub 1$(3s$sub 2$--3p$sub 2$) line in such a way as to maximize the power at the lambda$sub 1$ 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.