Resonant Bound-Free Contributions to Thomson Scattering of X-rays by Warm Dense Matter

TL;DR

This paper investigates how bound-free resonances, related to continuum lowering, influence X-ray Thomson scattering spectra in warm dense matter, revealing element-specific spectral features across the periodic table.

Contribution

It demonstrates the significance of bound-free resonances due to continuum lowering in X-ray scattering, extending predictions across multiple elements.

Findings

Resonances occur below bound-state thresholds in chromium.

D-state resonances dominate the bound-free structure function.

Similar resonant features are found in elements between Ca and Mn.

Abstract

Recent calculations [Nilsen et al. arXiv:1212.5972] predict that contributions to the scattered photon spectrum from 3s and 3p bound states in chromium (Z=24) at metallic density and T=12 eV resonate below the respective bound-state thresholds. These resonances are shown to be closely related to continuum lowering, where 3d bound states in the free atom dissolve into a resonant l=2 partial wave in the continuum. The resulting d-state resonance dominates contributions to the bound-free dynamic structure function, leading to the predicted resonances in the scattered X-ray spectrum. Similar resonant features are shown to occur in all elements in the periodic table between Ca and Mn (20 <= Z <= 25).