Adaptive Algorithm for the Generation of Superconfigurations in Hot-Plasma Opacity Calculations

Abstract

In hot plasmas, such as the ones encountered in astrophysics or laser-fusion studies, the number of ionic excited states may become huge, and the relevant electron configurations cannot always be handled individually. The Super Transition Array approach enables one to calculate the massic photo-absorption cross-section (or radiative opacity) in a statistical manner consisting of grouping configurations close in energy into superconfigurations. One of the main issues of the method, beyond its spectral resolution, is the determination of the most relevant configurations that contribute to opacity. In this work, we discuss different aspects of the generation of superconfigurations in a hot plasma and propose a new adaptive algorithm.

Multi-Configuration Calculation of Ionization Potential Depression

“…A superconfiguration [51,52] is an ensemble of configurations. The superconfiguration approximation consists in partitioning the ensemble of configurations, i.e., in gathering them into groups.…”

“…The superconfiguration approximation consists in partitioning the ensemble of configurations, i.e., in gathering them into groups. A superconfiguration represents a number of configurations of the plasma and is composed by an ensemble of supershells (i.e., groups of subshells) and their respective populations [51,52]. For example, superconfiguration Ξ = (1s2s2p) 10 (3s3p3d) 18 (4s4p4d4 f 5s5p5d) 19 (5 f 5g) 3 represents all the configurations with shells n = 1, n = 2 and n = 3 full, a total of 19 electrons distributed in all possible ways (consistent with the Pauli exclusion principle) in the subshells 4s, 4p, 4d, 4 f , 5s, 5p and 5d (the third supershell consists of 7 orbitals 4s to 5d), and 3 electrons in the last supershell made of subshells 5 f and 5g only.…”