A consistent approach for mixed detailed and statistical calculation of opacities in hot plasmas

Abstract

Absorption and emission spectra of plasmas with multicharged-ions contain transition arrays with a huge number of coalescent electricdipole (E1) lines, which are well suited for treatment by the unresolved transition array and derivative methods. But, some transition arrays show detailed features whose description requires diagonalization of the Hamiltonian matrix. We developed a hybrid opacity code, called SCORCG, which combines statistical approaches with fine-structure calculations consistently. Data required for the computation of detailed transition arrays (atomic configurations and atomic radial integrals) are calculated by the super-configuration code SCO (SuperConfiguration Opacity), which provides an accurate description of the plasma screening effects on the wave-functions. Level energies as well as position and strength of spectral lines are computed by an adapted RCG routine of R. D. Cowan. The resulting code provides opacities for hot plasmas and can handle mid-Z elements. The code is also a powerful tool for the interpretation of recent laser and Z -pinch experimental spectra, as well as for validation of statistical methods.

Detailed Opacity Calculations for Astrophysical Applications

“…Calculations of the free-free cross-section involve quantities related to the elastic-scattering matrix elements for electron-impact excitation of ions. The detailed (fine-structure) opacity code SCO-RCG [16][17][18] enables one to compute precise opacities for the calculation of accurate Rosseland means (see Section 3.2). The (super-)configurations are generated by the SCO code [19] on the basis of a statistical fluctuation theory (see the details below) and a self-consistent computation of atomic structure is performed for all the configurations.…”

“…As an example, the hydrogen H β profile computed by SCO-RCG at the conditions of Wiese et al is shown in Figure 24, right. For more complex ions, a cruder approach is used [16].…”

Accounting for highly excited states in detailed opacity calculations

“…These methods were proposed to address the aforementioned issue in a pragmatic manner. In section 3, the detailed opacity code SCO-RCG [7,8] is briefly described. The statistical approach that is currently used in the code to model those Rydberg spectators is explained.…”

Theoretical interpretation for 2p−ndabsorption spectra of iron, nickel, and copper in X-ray range measured at the LULI2000 facility

“…The recent experiment performed on the LULI2000 facility [4] aimed at checking a similar effect at fixed T but varying the atomic number Z: at T ∼ 20 eV, the 2p − 3d splitting is expected to vanish when Z decreases from 29 (Cu) to 26 (Fe). To describe this experiment, several models have been used and compared [5]: a statistical analysis with the superconfiguration code SCO [6], detailed-level accounting approaches using either HULLAC [7] or FAC [8] packages, the mixed approach SCO-RCG [9] combining the SCO approach with a detailed line analysis based on Cowan's code, and the collisional-radiative code SCRIC [10] suited to characterize the non-local-thermodynamic-equilibrium effects. It turned out that HULLAC a e-mail: michel.poirier@cea.fr This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.…”