EXTREME-UV PHOTOABSORPTION SPECTRUM OF A LASER-PRODUCED SILICON PLASMA - EVIDENCE FOR METASTABLE SI+ IONS

Time- and space-resolved extreme ultraviolet (XUV) photoabsorption spe ctra of a laser-produced silicon plasma have been recorded using a dua l-laser-produced plasma technique. Under appropriate experimental cond itions we have been able to measure structure due to 2p-subshell excit ation from metastable quartet states of the 2p(6)3s3p(2) configuration . The experimental spectrum is compared to a spectrum synthesized with computed data from the Cowan suite of atomic structure codes. Eigenve ctor data from the atomic structure calculations performed in LS coupl ing are used to assign most of the observed resonance structures and a number of the 2p-subshell ionization limits of atomic silicon are inf erred from the experimental data.