Coulomb (Velocity) Gauge Recommended in Multiconfiguration Calculations of Transition Data Involving Rydberg Series
by
Asimina Papoulia 1,2,*
, Jörgen Ekman 1, Gediminas Gaigalas 3, Michel Godefroid 4, Stefan Gustafsson 1, Henrik Hartman 1, Wenxian Li 1, Laima Radžiūtė 3, Pavel Rynkun 3, Sacha Schiffmann 2,4, Kai Wang 5 and Per Jönsson 1
Asimina Papoulia 1,2,*, Jörgen Ekman 1, Gediminas Gaigalas 3, Michel Godefroid 4, Stefan Gustafsson 1, Henrik Hartman 1, Wenxian Li 1, Laima Radžiūtė 3, Pavel Rynkun 3, Sacha Schiffmann 2,4, Kai Wang 5 and Per Jönsson 1
1
Department of Materials Science and Applied Mathematics, Malmö University, SE-20506 Malmö, Sweden
2
Division of Mathematical Physics, Department of Physics, Lund University, SE-22100 Lund, Sweden
3
Institute of Theoretical Physics and Astronomy, Vilnius University, Saulėtekio av. 3, LT-10222 Vilnius, Lithuania
4
Chimie Quantique et Photophysique, Université libre de Bruxelles, B-1050 Brussels, Belgium
5
Hebei Key Lab of Optic-electronic Information Materials, College of Physics Science and Technology, Hebei University, Baoding 071002, China
*
Author to whom correspondence should be addressed.
Atoms 2019, 7(4), 106; https://doi.org/10.3390/atoms7040106
Received: 23 October 2019 / Revised: 16 November 2019 / Accepted: 21 November 2019 / Published: 26 November 2019
(This article belongs to the Special Issue 13th International Colloquium on Atomic Spectra and Oscillator Strengths for Astrophysical and Laboratory Plasmas)
Astronomical spectroscopy has recently expanded into the near-infrared (nIR) wavelength region, raising the demands on atomic transition data. The interpretation of the observed spectra largely relies on theoretical results, and progress towards the production of accurate theoretical data must continuously be made. Spectrum calculations that target multiple atomic states at the same time are by no means trivial. Further, numerous atomic systems involve Rydberg series, which are associated with additional difficulties. In this work, we demonstrate how the challenges in the computations of Rydberg series can be handled in large-scale multiconfiguration Dirac–Hartree–Fock (MCDHF) and relativistic configuration interaction (RCI) calculations. By paying special attention to the construction of the radial orbital basis that builds the atomic state functions, transition data that are weakly sensitive to the choice of gauge can be obtained. Additionally, we show that the Babushkin gauge should not always be considered as the preferred gauge, and that, in the computations of transition data involving Rydberg series, the Coulomb gauge could be more appropriate for the analysis of astrophysical spectra. To illustrate the above, results from computations of transitions involving Rydberg series in the astrophysically important C IV and C III ions are presented and analyzed.
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Keywords:
infrared spectra; spectrum calculations; multiconfiguration methods; Rydberg series; Rydberg states; electric dipole transitions; transition rates; Babushkin gauge; Coulomb gauge; length form; velocity form
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MDPI and ACS Style
Papoulia, A.; Ekman, J.; Gaigalas, G.; Godefroid, M.; Gustafsson, S.; Hartman, H.; Li, W.; Radžiūtė, L.; Rynkun, P.; Schiffmann, S.; Wang, K.; Jönsson, P. Coulomb (Velocity) Gauge Recommended in Multiconfiguration Calculations of Transition Data Involving Rydberg Series. Atoms 2019, 7, 106.
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