Plasma broadening of autoionizing resonances

TL;DR

This paper develops a comprehensive theoretical framework to analyze how plasma environments significantly broaden and shift atomic autoionizing resonances, affecting photoionization and opacity in high-energy-density conditions.

Contribution

It introduces a general formulation and computational method that accounts for multiple broadening mechanisms affecting autoionizing resonances in plasma environments.

Findings

Plasma effects cause significant broadening and shifting of AI resonances.

Resonance strengths are redistributed but conserved as continua with increasing density.

The method is applicable to high-energy-density plasmas like fusion and stellar interiors.

Abstract

A general formulation is developed to demonstrate that atomic autoionizing (AI) resonances are broadened and shifted significantly due to plasma effects across bound-free continua. The theoretical and computational method presented accounts for broadening mechanisms: electron collisional, ion microfields (Stark), thermal Doppler, core excitations, and free-free transitions. {\it Extrinsic} plasma broadening redistributes and shifts AI resonance strengths while broadly preserving naturally {\it intrinsic} asymmetries of resonance profiles. Integrated oscillator strengths are conserved as resonance structures dissolve into continua with increasing electron density. As exemplar, the plasma attenuation of photoionization cross sections computed using the R-matrix method is studied in neon-like Fe~XVII in a critical range $N_e = 10^{21-24}$cc along isotherms $T = 1-2 \times 10^6$K, and its impact on Rosseland Mean opacities. The energy-temperature-density dependent cross sections would elicit and introduce physical features in resonant processes in photoionization, \eion excitation and recombination. The method should be generally applicable to atomic species in high-energy-density (HED) sources such as fusion plasmas and stellar interiors.