Authors

Abstract

We report on an experimental and theoretical study of double K-shell photoionization of Ne over the 2.38.5 keV x-ray energy range. The ratio of double-to-single K-shell photoionization cross sections was determined experimentally by measuring the relative rates of the KKKL2,3L2,3 (2D) Auger hypersatellite and the KL2,3L2,3 (1D) diagram Auger transitions. By scaling the hypersatellite-diagram Auger-electron ratios to KK/K cross-section ratios, comparison was made with theoretical cross-section ratios of He-like Ne8+ determined by the R matrix with pseudostates method. The experimental Ne and theoretical Ne8+ cross-section ratios show similar variations with energy, but the experimental ratios systematically exceed the calculated ratios and also show a lower threshold energy for double K-shell photoionization onset compared to the computed Ne8+ threshold. The discrepancy is attributed to effects of L-shell electrons not included in the He-like Ne8+ calculations. Quantified scaling with nuclear charge Z along the He-like isoelectronic sequence indicates that the measured 10-electron Z=10 double K-shell photoionization cross section behaves like the computed He-like Z=8.9 cross section, suggesting an effective nuclear screening parameter of sL=1.1 by the additional eight outer L-shell electrons. Experimental results for the energy variations of Auger electron transitions from other multielectron hole states are also discussed.