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Coulomb (Velocity) Gauge Recommended in Multiconfiguration Calculations of Transition Data Involving Rydberg Series

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Department of Materials Science and Applied Mathematics, Malmö University, SE-20506 Malmö, Sweden
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Division of Mathematical Physics, Department of Physics, Lund University, SE-22100 Lund, Sweden
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Institute of Theoretical Physics and Astronomy, Vilnius University, Saulėtekio av. 3, LT-10222 Vilnius, Lithuania
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Chimie Quantique et Photophysique, Université libre de Bruxelles, B-1050 Brussels, Belgium
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Hebei Key Lab of Optic-electronic Information Materials, College of Physics Science and Technology, Hebei University, Baoding 071002, China
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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
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. View Full-Text
Keywords: infrared spectra; spectrum calculations; multiconfiguration methods; Rydberg series; Rydberg states; electric dipole transitions; transition rates; Babushkin gauge; Coulomb gauge; length form; velocity form 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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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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