Velocity and electronic state distributions of sputtered Fe atoms by laser-induced fluorescence spectroscopy

Abstract

Velocity distributions and relative populations in the fine-structure levels of the a 5DJ ground state of Fe atoms, produced by sputtering with 3 keV argon ions, have been investigated by Doppler-shifted laser-induced fluorescence. The laser system employs a single-mode, scanning ring dye laser, amplified by a sequence of three excimer-pumped flowing dye cells. Frequency doubling in a KD*P crystal was used to produce high energy (>0.5 mJ) pulses of narrowband tunable UV output near 300 nm. Laser power influence on effective velocity bandwidth was investigated. Favorable light-collection geometry minimized distortion of the velocity spectra from apparatus-averaging effects. In impurity flux diagnostic applications in fusion devices, substantial spatial averaging may occur. In the latter case, the narrow velocity bandwidth (70 m/s, transform limit) of the present laser system is particularly useful.