Summation of the spectra of all partially resolved transition arrays in a supertransition array

Kurzweil, Yair; Hazak, G.

doi:10.1103/physreve.94.053210

Cited by 17 publications

(15 citation statements)

References 19 publications

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“…This enabled us to obtain very detailed spectra, which were successfully compared to many recent laser and Z-pinch measurements. The STA formalism is still the cornerstone of several opacity codes, and new ideas are emerging, such as the CRSTA approach [44][45][46] or the extension to the superconfiguration approach of the PRTA model [40,76].…”

Section: Discussionmentioning

confidence: 99%

“…The contribution of the Rydberg supershell is included as a Gaussian "dressing function" [40]. We also have the possibility to replace this dressing function by a coarse-grain configurationally resolved profile, following the configurationally resolved super transition array (CRSTA) method of Kurzweil et al [44][45][46] (see Section 6.1).…”

Section: The Beginning Of a New Story: The Birth Of Sco-rcg Codementioning

confidence: 99%

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Super Transition Arrays: A Tool for Studying Spectral Properties of Hot Plasmas

Pain

2021

Plasma

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For the theoretical study of X and extreme-UV spectra of ions in plasmas, quantum mechanics brings more detailed results than statistical physics. However, it is impossible to handle individually the billions of levels that must be taken into account in order to properly describe hot plasmas. Such levels can be gathered into electronic configurations or superconfigurations (groups of configurations) and the corresponding calculations rely on appropriate statistical methods, for local or non-local thermodynamic equilibrium plasmas. In this article we present the basic principles of the Super-Transition-Array approach as well as its practical implementation. During the last decades, calculations performed with the SCO code (Superconfiguration Code for Opacity) have been compared to opacity measurements. The code includes static screening of ions by plasma and is well suited for studying plasma density effects (for example pressure ionization) on opacity and equation of state. The recently developed SCO-RCG code (Superconfiguration Code for Opacity combined with Robert Cowan’s “G” subroutine) combines statistical methods from SCO and fine-structure (detailed-level-accounting) calculations using subroutine RCG from Cowan’s code. SCO-RCG enables us to obtain very detailed spectra and to significantly improve the interpretation of experimental spectra. The Super-Transition-Array formalism is still the cornerstone of several opacity codes, and new ideas are emerging, such as the Configurationally Resolved-Super-Transition-Array approach or the extension of the Partially Resolved-Transition-Array concept to the superconfiguration method.

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Section: Discussionmentioning

confidence: 99%

Section: The Beginning Of a New Story: The Birth Of Sco-rcg Codementioning

confidence: 99%

Super Transition Arrays: A Tool for Studying Spectral Properties of Hot Plasmas

Pain

2021

Plasma

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“…In the STA method [28,33,[46][47][48][49][50][51][52][53], a large number of configurations C are grouped into super-configurations (SCs), commonly denoted by Ξ = Π σ σ Qσ , which are defined as sets of configurations which have Q σ electrons in each 'supershell' σ, which is a group of shells. The total occupation of a super configuration is naturally:…”

Section: Number Configurations Within Superconfigurationsmentioning

confidence: 99%

Number of populated electronic configurations in a hot dense plasma

Krief

2021

Phys. Rev. E

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In hot dense plasmas of intermediate or high-Z elements in the state of local thermodynamic equilibrium, the number of electronic configurations contributing to key macroscopic quantities such as the spectral opacity and equation of state, can be enormous. In this work we present systematic methods for the analysis of the number of relativistic electronic configurations in a plasma. While the combinatoric number of configurations can be huge even for mid-Z elements, the number of configurations which have non negligible population is much lower and depends strongly and nontrivially on temperature and density. We discuss two useful methods for the estimation of the number of populated configurations: (i) using an exact calculation of the total combinatoric number of configurations within superconfigurations in a converged super-transition-array (STA) calculation, and (ii) by using an estimate for the multidimensional width of the probability distribution for electronic population over bound shells, which is binomial if electron exchange and correlation effects are neglected. These methods are analyzed, and the mechanism which leads to the huge number of populated configurations is discussed in detail. Comprehensive average atom finite temperature density functional theory (DFT) calculations are performed in a wide range of temperature and density for several low, mid and high Z plasmas. The effects of temperature and density on the number of populated configurations are discussed and explained.

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“…In these methods, the transition array between two configurations is usually reduced to a single Gaussian but can be replaced by a sum of partially resolved transition arrays represented by Gaussians [79,80] that are then sampled statistically to simulate detailed line accounting [81]. For heavy ions where UTAs still fall short, a higher-level extension referred to as the super-transition-array (STA) method involves the grouping of many configurations into a single superconfiguration, whereby the UTA summation to a single STA can be performed analytically [82][83][84]. Recent STA calculations of the RMO in the solar convection zone boundary agree very well with both OP and OPAL, and predict a meager heavy-element (Z > 28) contribution [26].…”

Section: Atomic Opacities Recent Developmentsmentioning

confidence: 99%

Computation of Atomic Astrophysical Opacities

Mendoza

2018

Atoms

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Abstract:The revision of the standard Los Alamos opacities in the 1980-1990s by a group from the Lawrence Livermore National Laboratory (OPAL) and the Opacity Project (OP) consortium was an early example of collaborative big-data science, leading to reliable data deliverables (atomic databases, monochromatic opacities, mean opacities, and radiative accelerations) widely used since then to solve a variety of important astrophysical problems. Nowadays the precision of the OPAL and OP opacities, and even of new tables (OPLIB) by Los Alamos, is a recurrent topic in a hot debate involving stringent comparisons between theory, laboratory experiments, and solar and stellar observations in sophisticated research fields: the standard solar model (SSM), helio and asteroseismology, non-LTE 3D hydrodynamic photospheric modeling, nuclear reaction rates, solar neutrino observations, computational atomic physics, and plasma experiments. In this context, an unexpected downward revision of the solar photospheric metal abundances in 2005 spoiled a very precise agreement between the helioseismic indicators (the radius of the convection zone boundary, the sound-speed profile, and helium surface abundance) and SSM benchmarks, which could be somehow reestablished with a substantial opacity increase. Recent laboratory measurements of the iron opacity in physical conditions similar to the boundary of the solar convection zone have indeed predicted significant increases (30-400%), although new systematic improvements and comparisons of the computed tables have not yet been able to reproduce them. We give an overview of this controversy, and within the OP approach, discuss some of the theoretical shortcomings that could be impairing a more complete and accurate opacity accounting.

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Summation of the spectra of all partially resolved transition arrays in a supertransition array

Cited by 17 publications

References 19 publications

Super Transition Arrays: A Tool for Studying Spectral Properties of Hot Plasmas

Super Transition Arrays: A Tool for Studying Spectral Properties of Hot Plasmas

Number of populated electronic configurations in a hot dense plasma

Computation of Atomic Astrophysical Opacities

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