A plea for a reexamination of ionization potential depression measurements

Experiments at the Linac Coherent Light Source determined the ionization potential depression (IPD) in dense plasmas by measuring the K alpha fluorescence associated with K-shell holes created by the X-ray free-electron laser. The analysis of the experimental spectrum found a significantly larger IPD than predicted by the widely used Stewart-Pyatt model. It is shown, however, that a more accurate treatment of atomic levels than used in the analysis has additional channels reducing the threshold laser energy for creating K alpha photons without invoking an increase in the IPD. Thus, it is argued that a simulation of the Ka fluorescence using improved atomic data could impact the interpretation of the experimental results. (C) 2014 Elsevier B.V. All rights reserved.