Relativistic Corrections to H, O(VII), and Fe(XXV) Lineshapes in Hot Plasmas

Author

• Asa Drew Dawdy McNaughton, Portland State UniversityFollow

Sponsor

Portland State University. Department of Physics

First Advisor

Erik Sanchez

Term of Graduation

Spring 2026

Date of Publication

5-18-2026

Document Type

Thesis

Degree Name

Master of Science (M.S.) in Physics

Department

Physics

Language

English

Subjects

Lineshapes, Opacity, Plasma, Relativistic corrections, Solar core, Spectroscopy

Physical Description

1 online resource (x, 113 pages)

Abstract

An extension of theoretical Stark broadening for spectral lines in hot plasmas is developed with corrections for close-in and relativistic interactions between plasma electrons and radiating atoms/ions. The analytical framework followed is the semi- classical 'impact' theory of line broadening developed by Griem, the standard in the field. We develop the relativistic model analytically by describing the free electron's interaction as a perturbation of the radiating system with the first-order relativistic Breit Hamiltonian. The relativistic part of electron broadening scales with electron temperature T_e^3/2 and has only weak dependence on electron density N_e. Lineshape models considering only the electrostatic plasma-atom interaction scale with 1/√T_e and linearly with N_e. Consequently, relativistic effects consti- tute a significant, even dominant electron broadening mechanism for medium-Z ion (here, Fe(XXV)) K-α transitions for hot plasmas of moderate or less density. Relativistic corrections increase spectral line broadening in the line core and enhance brightness in the wings of the line compared to electrostatic-only predictions. This effect is strong enough that lineshapes from hot, less dense plasmas (usually considered effectively transparent) could be misinterpreted as coming from much denser, cooler plasmas. This result motivates further investigation into relativistic effects on spectral line broadening in hot plasmas.

Rights

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Persistent Identifier

https://archives.pdx.edu/ds/psu/44909

Recommended Citation

McNaughton, Asa Drew Dawdy, "Relativistic Corrections to H, O(VII), and Fe(XXV) Lineshapes in Hot Plasmas" (2026). Dissertations and Theses. Paper 7104.