Measurements of continuum lowering in solid-density plasmas created from elements and compounds


The effect of a dense plasma environment on the energy levels of an embedded ion is usually described in terms of the lowering of its continuum level. Using the tunable x-ray free-electron laser, we have carried out an experiment showing that the standard density-dependent analytical models are inadequate to describe solid-density plasmas at the temperatures studied. These results are important for astrophysics, planetology, and inertial confinement fusion.

The reduction in the ionization potential of Mg, Al and Si in the different materials is plotted as a function of the ionic charge state and is compared with the predictions of analytical models. The figure demonstrates the insensitivity of the measured IPDs for Al and Si to the different environment in different materials and the mismatch between experimental results and theoretical predictions obtained by using standard density-dependent analytical models.