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 et al [High Energy Density Phys. 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.

The synthetic emission spectra and opacity of high-density, high-temperature germanium (Z=32) plasma from super-transition-array (STA) calculations are presented. The viability of the STA model, which is based on a statistical superconfigurations accounting approach for calculating the atomic and radiative properties, is examined by comparing and contrasting its results against the available experimental data and other theoretical calculations. First, we focus on the emission data.To model the data, the Eulerian radiation-hydrodynamics code FastRad3D is used in conjunction with STA to obtain the STA-required inputs, namely, the time-dependent temperature and density profiles of the Ge plasmas. Consequently, we find that STA results fit the experimental spectrum reasonably well, reproducing the main spectral features of 2p − 3d, 2s − 3p, and 2p − 4d transitions from the laser-heated germanium layer buried in plastic [High Energy Density Phys., 6 (2010) 105]. However, careful comparison between experimental and theoretical results in the photonenergy regions of ∼1.7 keV shows some degrees of disparity between the two. This may be due to the non-LTE effects and the presence of spatial gradients in the sample. Limitations of STA to model the experimental spectrum precisely is expected and underscoring the difficulty of the present attempts as the model assumed local thermodynamics equilibrium population dynamics.Second, we examine the STA calculated multi-frequency opacities for a broad range of Ge plasma conditions covering the L-and M-shell spectral range. Comparing with a hybrid LTE opacity code which combines the statistical super-transition-array and fine-structure methods [High Energy Density Phys., 7 (2011) 234], impressively good agreement is found between the two calculations. In addition, the sensitivity of the opacity results in various plasma temperatures and mass densities is discussed. The ionized population fraction and average ionization of the Ge plasma are also described. Comparisons of STA results in the observed spectrum and opacity are considerably close while offering the advantage of computational speed and its capability of treating hot and dense high-Z plasmas.