EVEN-PARITY AUTOIONIZING STATES IN THE EXTREME-ULTRAVIOLET PHOTOABSORPTION SPECTER OF MG, AL+, AND SI2+

The dual-laser-produced plasma (DLP) photoabsorption technique has bee n used to study 2p --> 3s excitations in the isoelectronic species Mg, Al+, and Si2+ prepared in the excited configuration 2p(6)3s3p. The au toionizing upper states belong to the 2p(5)3s(2)3p even-parity configu ration. The versatility of the technique is demonstrated through a car eful combination of space- and time-resolved photoabsorption scans. Pl asma conditions optimized for the observation of the inaccessible pari ty regime were successfully reproduced along the isoelectronic,sequenc e of interest. All the observed transitions were interpreted with the help of multiconfigurational atomic structure calculations. In the cas e of magnesium, the photoabsorption data are compared with the ejected -electron spectra excited by low-energy electron impact of Pejcev et a l. [J. Phys. B 10, 2389 (1977)].