In the course of conducting laser–target interaction experiments at 20-ps pulse length using Al and Mg targets, to determine the ionization balance of these elements, time-resolved K-shell spectral line strengths were obtained, suggesting population inversions between excited levels in both He-like and H-like ions. Effects of resonance-line opacities need to be analyzed in more detail, but opacity effects alone do not account for the anomalous line-intensity ratios that are observed to persist 200–300 ps after the laser pulse. Comparisons with 50-ps and 100-ps pulse shots do not show evidence of inversion, although nonequilibrium spectral lineintensity distributions are observed.
© 1992 Optical Society of America
G. Charatis, N. D. Delamater, Gar. E. Busch, R. A. Bosch, G. G. Ganger, J. L. Thornburg, J. R. Brundage, D. Sullivan, H. A. Neal, Jr., R. L. Shephard, C. J. Keane, A. L. Osterheld, D. C. Eder, and D. L. Matthews, "Evidence for population inversions in Al and Mg by laser irradiation at 20-ps pulse lengths," J. Opt. Soc. Am. B 9, 1278-1282 (1992)