Optical diagnostics of lead and PbGa2S4 layered crystal laser plasmas

Abstract

Laser plasmas produced at the surfaces of lead and a PbGa2S4 layered crystal irradiated by a neodymium laser with λ=1.06 µm, pulse duration τ=20 ns, and intensity W=(1–2)×109 W/cm2 are studied using optical diagnostics. It is shown that, in a lead plasma, the most intense (characteristic) lines are the PbI 405.7-nm, PbI 368.3-nm, PbI 364-nm, and PbII 220.4-nm lines. In a layered crystal plasma, the emission spectrum is an aggregation of the most intense PbI and GaI lines, whereas sulfur lines are absent. The bottlenecks of the recombination of the ionic and atomic components of the lead and PbGa2S4 crystal plasmas are determined. The average propagation velocity of the lead laser plume is 18–20 km/s. A comparative analysis of the emission dynamics of PbI and GaI lines in the laser plasmas of these metals and in the plasma of a PbGa2S4 crystal is carried out. The results obtained are important for the optical diagnostics of the plasmas of leadand gallium-containing crystals and for the optimization of laser deposition of the thin films of these substances.