A 2-photon LIF study on the expansion behaviour of a plasma beam generated from a mixture of Ar and H/sub 2/

In an expanding plasma created by a cascaded arc from a Ar-H/sub 2/ mixture, spatially resolved densities, temperatures, and velocities of ground state atomic hydrogen are obtained by applying two-photon excitation laser induced fluorescence. The axial velocity profile of H indicates a strong coupling between Ar and H atoms. However, the atomic hydrogen density and temperature profiles cannot be fully described in terms of a supersonic expansion model in contrast with the profiles of Ar. There are several indications that hydrogen atoms can escape the supersonic domain by a scattering proces