The vuv photodissociation of OCS in an argon matrix at 5 K has been shown to yield S(1S) atoms. The S(1S –1D) emission is observed only during the irradiation and does not appear when CS2 is photolyzed under the same conditions. However, in both cases the thermoluminescence which follows an increase of the matrix temperature is due to the S2(B 3Σu−→X 3Σg−) radiative transition. This substantiates the fact that S atoms do indeed diffuse in an argon matrix already at 6 K. Furthermore, the (a 3Π→X 1Σ+) emission of CS is observed both during the CS2 irradiation and as thermoluminescence. This last observation suggests that C atoms can also diffuse under these conditions at about the same rate as the diffusion rate of N atoms in N2 matrix, measured by Brocklehurst and Pimentel.

A multiphoton (2+1) absorption laser-induced fluorescence diagnostic is employed for determination of the spatial distribution of atomic hydrogen density in the post-discharge of a low-pressure microwave-induced H2 plasma, using one pulsed frequency-doubled dye laser. H atom density profiles are described by a simple diffusion equation and the probability of recombination of H atoms on silica is deduced from the profiles.

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