Radiative and atomic properties of C and CH plasmas in the warm-dense matter regime

TL;DR

This paper employs the super transition arrays (STA) method to model the radiative and atomic properties of carbon and CH plasmas in the warm-dense matter regime, benchmarking against experiments and other theories.

Contribution

It introduces the application of STA to C and CH plasmas in the warm-dense regime, validating results with experimental data and advanced theoretical methods.

Findings

STA results agree well with Dirac-Fock and Hartree-Fock-Slater theories for carbon.

STA-derived opacities match quantum-molecular-dynamics and Hartree-Fock results for CH at temperatures above 20 eV.

The model's predictions are consistent with experimental measurements within uncertainties.

Abstract

A theoretical model based on the method of super transition arrays (STA) is used to compute the emissivities, opacities and average ionization states of carbon (C) and polystyrene (CH) plasmas in the warm-dense matter regime in which the coupling constant varies between 0.02 to 2.0. The accuracy of results of STA calculations is assessed by benchmarking against the available experimental data and results obtained using other theoretical methods, assuming that a state of local thermodynamic equilibrium exists in the plasma. In the case of a carbon plasma, the STA method yields spectral features that are in reasonably-good agreement with Dirac-Fock and Hartree-Fock-Slater theories; in the case of CH, we find that STA-derived opacities are very similar to those derived using quantum-molecular-dynamics density-functional theory and Hartree-Fock method down to plasma temperature of about 20 eV. Our calculations also compare favorably with available experimental measurements of Gamboa {\it et al} [High Energy Density Phys. {\bf 11}, 75 (2014)] of the plasma temperature and average ionization state behind a blast wave in a pure carbon foam. Although the STA-computed average-ionization charge state in the rarefaction region appears to be lower than the experimental data, it is within the experimental uncertainty and the discrepancy is nevertheless consistent with results reported using an atomic kinetic model. In addition, we further predict the temperature dependence of average ionization states of CH plasma in the same temperature range as for the carbon plasma.