Accounting for highly excited states in detailed opacity calculations

Abstract

In multiply-charged ion plasmas, a significant number of electrons may occupy high-energy orbitals. These "Rydberg" electrons, when they act as spectators, are responsible for a number of satellites of X-ray absorption or emission lines, yielding a broadening of the red wing of the resonance lines. The contribution of such satellite lines may be important, because of the high degeneracy of the relevant excited configurations which give these large Boltzmann weights. However, it is in general difficult to take these configurations into account since they are likely to give rise to a large number of lines. We propose to model the perturbation induced by the spectators in a way similar to the PartiallyResolved-Transition-Array approach recently published by C. Iglesias. It consists in a partial detailedline-accounting calculation in which the effect of the Rydberg spectators is included through a shift and width, expressed in terms of the canonical partition functions, which are key-ingredients of the SuperTransition-Arrays model. The resulting method can a priori be used in any detailed-configuration/lineaccounting opacity code.

A New Generation of Los Alamos Opacity Tables

“…Long-term intensive efforts to produce accurate and comprehensive opacity tables have been underway for many years, with notable efforts being the Opacity Project (OP; Seaton et al 1994;Seaton & Badnell 2004;Badnell et al 2005), the Lawrence Livermore National Laboratory OPAL opacity tables (Rogers & Iglesias 1992;Iglesias & Rogers 1996), and more recently the opacity tables produced using the OPAS code (Blancard et al 2012).The OPAS code has very recently been used to compute opacities for solar mixtures (Le Pennec et al 2015;Mondet et al 2015), and improved agreement with helioseismic observations was reported. The SCO-RCG code (Pain & Gilleron 2015) also appears to be a powerful method with which to compute opacities. At Los Alamos National Laboratory (LANL), tables of opacities have been computed using the LEDCOP code (Magee et al 1995) in the 1990s and these OPLIB tables have successfully been used in solar modeling (Neuforge-Verheecke et al 2001;.…”

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.…”

“…We have extended this approach to the STA formalism [25], consisting in omitting the Rydberg supershell in the computation, and adding its contribution to the widths of all lines. The contribution of the Rydberg supershell is included as a Gaussian "dressing function" [17]. We have also the possibility to replace this dressing function by a coarse grained configurationally resolved profile, following the CRSTA (Configurationally Resolved Transition Array) method [26].…”

“…However, it is in general difficult to take those configurations into account since they are likely to give rise to a large number of lines. We proposed to model the perturbation induced by the spectators in a detailed way, inspired by the Partially Resolved Transition Array approach recently published by Iglesias [69,70], and extended to the STA theory [17,71]. This approach, based on the additivity of the variances from active and spectator electrons in the STA theory, consists in a reduced detailed-line-accounting calculation, omitting these Rydberg electrons, the effect of the latests being included through an additional shift and broadening of the lines, expressed in terms of canonical partition functions, key-ingredients of the STA model.…”

“…OP [42,43] 0.59 R-matrix [75,76] 0.51 ATOMIC [39,40] 0.60 OPAS [82][83][84] 0.70 SCO-RCG [17] 0.64 SCRAM [85] 0.77 TOPAZ [86,87] 0.62 Cold [72] 0.75…”