Absorption and stimulated emission between the electronic states of C and C2radicals in an expanding thermal plasma

Using the method of reabsorption the absolute densities of argon, atomic and molecular carbon are determined during the deposition of amorphous hydrogenated (diamond-like) carbon coatings by an expanding thermal are plasma. Depending on the gas mixture argon/methane or argon/acetylene and the manner of hydrocarbon injection, the stationary negative or positive absorption between the quantum states Ar(3p 5 4p to 3p 5 4s). C(2p3s to 2p 2 ) and C 2 (d 3 Pi g , v'=0 to a 3 Pi u , v''=0) were obtained. From the line absorption the absolute population densities of the radicals in the plasma have been determined. The density of the argon first excited state Ar(3p 5 4s, 3 P 2 ) is approximately=10 16 -10 17 m -3 the atomic and diatomic molecular carbon densities are of the order of 10 18 -10 19 m -3 .