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Atoms 2017, 5(1), 3; doi:10.3390/atoms5010003

Combining Multiconfiguration and Perturbation Methods: Perturbative Estimates of Core–Core Electron Correlation Contributions to Excitation Energies in Mg-Like Iron

1
Materials Science and Applied Mathematics, Malmö University, SE-205 06 Malmö, Sweden
2
Department of Computer Science, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
3
Mathematical Institute, University of Oxford, Woodstock Road, Oxford OX2 6GG, UK
4
Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, Wilberforce Road, Cambridge CB3 0WA, UK
*
Author to whom correspondence should be addressed.
Academic Editor: Joseph Reader
Received: 25 November 2016 / Revised: 22 December 2016 / Accepted: 6 January 2017 / Published: 12 January 2017
(This article belongs to the Special Issue Spectra of Ionized Atoms: From Laboratory to Space)
View Full-Text   |   Download PDF [381 KB, uploaded 12 January 2017]

Abstract

Large configuration interaction (CI) calculations can be performed if part of the interaction is treated perturbatively. To evaluate the combined CI and perturbative method, we compute excitation energies for the 3 l 3 l , 3 l 4 l and 3 s 5 l states in Mg-like iron. Starting from a CI calculation including valence and core–valence correlation effects, it is found that the perturbative inclusion of core–core electron correlation halves the mean relative differences between calculated and observed excitation energies. The effect of the core–core electron correlation is largest for the more excited states. The final relative differences between calculated and observed excitation energies is 0.023%, which is small enough for the calculated energies to be of direct use in line identifications in astrophysical and laboratory spectra. View Full-Text
Keywords: excitation energies; multiconfiguration Dirac–Hartree–Fock; configuration interaction excitation energies; multiconfiguration Dirac–Hartree–Fock; configuration interaction
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Gustafsson, S.; Jönsson, P.; Froese Fischer, C.; Grant, I. Combining Multiconfiguration and Perturbation Methods: Perturbative Estimates of Core–Core Electron Correlation Contributions to Excitation Energies in Mg-Like Iron. Atoms 2017, 5, 3.

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