C vi Lyman line profiles from 10-ps KrF-laser-produced plasmas

Plasmas with densities {}10²² cm^-3 and electron temperatures Tₑ{}200 eV were produced near solid graphite targets that were laser irradiated at {~}10¹⁵ W/cm², with a {~}10¹¹ W/cm² prepulse from amplified spontaneous emission. Photographic spectra taken nearly side-on within {}0.1 mm from the target surface show strong H-like lines corresponding to n=2,3, and 4 to n=1 transitions and weaker He-like lines, with full width at half maximum widths {}4 eV. The Lyman-{α} line is optically thick. A five-layer model with high-electron-density and electron-temperature core layers and less dense and cooler outer layers was used for simulation. Central layers with high Tₑ contribute most of the emission while outside cooler layers cause an absorption dip in the central part of the Lyman-{α} line. Asymmetrical self-reversal is interpreted by radial expansion. A plasma-induced line shift was evident in some of the experimental line profiles, especially for the asymmetrical and strongly shifted Lyman-{γ} line of C vi ions. Time-dependent rate equations were solved for checking the assumed local-thermodynamic-equilibrium condition for plasmas with adiabatic expansion cooling.