Stark effect modeling in the detailed opacity code SCO-RCG

TL;DR

This paper introduces an advanced modeling approach for Stark broadening in plasma spectroscopy using the SCO-RCG code, incorporating detailed atomic data and relativistic effects to improve plasma diagnostics.

Contribution

The paper develops a detailed Stark effect modeling method within SCO-RCG for K-shell spectroscopy, including relativistic fine-structure and plasma environment effects.

Findings

Enhanced accuracy in Stark broadening predictions.

Comparison shows improvements over semi-empirical models.

Ability to analyze satellite line impacts.

Abstract

The broadening of lines by Stark effect is an important tool for inferring electron density and temperature in plasmas. Stark-effect calculations often rely on atomic data (transition rates, energy levels,...) not always exhaustive and/or valid for isolated atoms. We present a recent development in the detailed opacity code SCO-RCG for K-shell spectroscopy (hydrogen- and helium-like ions). This approach is adapted from the work of Gilles and Peyrusse. Neglecting non-diagonal terms in dipolar and collision operators, the line profile is expressed as a sum of Voigt functions associated to the Stark components. The formalism relies on the use of parabolic coordinates within SO(4) symmetry. The relativistic fine-structure of Lyman lines is included by diagonalizing the hamiltonian matrix associated to quantum states having the same principal quantum number $n$. The resulting code enables one to investigate plasma environment effects, the impact of the microfield distribution, the decoupling between electron and ion temperatures and the role of satellite lines (such as Li-like $1sn\ell n'\ell' - 1s^2n\ell$, Be-like, etc.). Comparisons with simpler and widely-used semi-empirical models are presented.