Density-matrix correlations in the relaxation theory of electron broadening

Journal Article · 16 July 2018 · Physical Review A

DOI: https://doi.org/10.1103/PhysRevA.98.012505 · OSTI ID:1507368

Gomez, Thomas A. ^[1]; Nagayama, Taisuke  ^[2]; Kilcrease, David P.  ^[3]; Montgomery, Michael H.  ^[4]; Winget, Donald E.  ^[4]

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1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); The University of Texas at Austin
2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
4. Univ. of Texas, Austin, TX (United States)

Spectral lines of radiating atoms are broadened by perturbations due to the surrounding plasma environment. In line-broadening calculations, the statistical average of the perturbation is weighted by the density matrix, which, in thermal equilibrium, contains correlations between the radiator and plasma. These correlations, however, have been neglected by all line-broadening theories except for the kinetic theory. The relaxation theory of line broadening is a mathematically exact derivation containing only one physical approximation: neglect of density- matrix correlations. We revisit this derivation and improve it by including the correlations. The line-broadening operator derived with the updated relaxation theory differs from that derived from the kinetic theory, though both derivations are considered to be exact. The kinetic theory derivation predicts that density-matrix correlations result a strong static shift of spectral lines. Our derivation, on the other hand, predicts that the correlations are a frequency-dependent effect that affects the line wings, and there is no shift of the line due to correlations. In addition, we predict that changes in the line shape due to correlations are only noticeable at extremely high densities. To distinguish the more appropriate model, we compare the shifts calculated with the relaxation and kinetic theory with data. The comparison shows support for the relaxation theory and casts into doubt the accuracy of the derivation of the kinetic theory of line broadening.

• Research Organization: Univ. of Texas, Austin, TX (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Contributing Organization: Dr. Carlos Iglesias, Dr. Stephanie Hansen, Dr. Andrew Baczewski, and Dr. Daniel Jensen for stimulating discussions; Marc Schaeuble for help with the manuscript.
• Grant/Contract Number: NA0003843
• OSTI ID: 1507368
• Journal Information: Physical Review A, Journal Name: Physical Review A Journal Issue: 1 Vol. 98; ISSN PLRAAN; ISSN 2469-9926
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English