Diagnostics of atoms by laser spectroscopic methods in plasmas and plasma-wall interaction studies (vacuum ultraviolet and two-photon techniques)

We describe in this paper the measurement of light atom concentrations in p lasmas and their detection in plasma-wall interaction experiments. VUV radi ation or multiphoton techniques are required due to the large energy differ ences between the ground state and the excited states. We discuss briefly c ommonly applied schemes of nonlinear optics to generate narrow-bandwidth tu nable VUV radiation with particular emphasis on high-order stimulated anti- Stokes Raman scattering in hydrogen gas. Applications of absorption and las er-induced fluorescence spectroscopy both to discharges and experiments wit h ion beams on targets are described. The discussion of multiphoton techniq ues focuses on the detection of sputtered atoms by resonantly enhanced mult iphoton ionization (REMPI) and the detection of O and H in radiofrequency e xcited plasma reactors. Methods of absolute calibration and limitations by collisional effects are considered in this context. Examples of the detecti on of atomic hydrogen by light mixing are outlined in the conclusion.