| 1. |
- Li, Wenxian, et al.
(författare)
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Multiconfiguration Dirac-Hartree-Fock calculations of Lande g-factors for ions of astrophysical interest : B II, C I-IV, Al I-II, Si I-IV, P II, S II, Cl III, Ar IV, Ca I, Ti II, Zr III, and Sn II
- 2020
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 639
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Tidskriftsartikel (refereegranskat)abstract
- Aims. The Lande g-factor is an important parameter in astrophysical spectropolarimetry, used to characterize the response of a line to a given value of the magnetic field. The purpose of this paper is to present accurate Lande g-factors for states in B II, C I-IV, Al I-II, Si I-IV, P II, S II, Cl III, Ar IV, Ca I, Ti II, Zr III, and Sn II.Methods. The multiconfiguration Dirac-Hartree-Fock and relativistic configuration interaction methods, which are implemented in the general-purpose relativistic atomic structure package GRASP2K, are employed in the present work to compute the Lande g-factors for states in B II, C I-IV, Al I-II, Si I-IV, P II, S II, Cl III, Ar IV, Ca I, Ti II, Zr III, and Sn II. The accuracy of the wave functions for the states, and thus the accuracy of the resulting Lande g-factors, is evaluated by comparing the computed excitation energies and energy separations with the National Institute of Standards and Technology (NIST) recommended data.Results. All excitation energies are in very good agreement with the NIST values except for Ti II, which has an average difference of 1.06%. The average uncertainty of the energy separations is well below 1% except for the even states of Al I; odd states of Si I, Ca I, Ti II, Zr III; and even states of Sn II for which the relative differences range between 1% and 2%. Comparisons of the computed Lande g-factors are made with available NIST data and experimental values. Analysing the LS-composition of the wave functions, we quantify the departures from LS-coupling and summarize the states for which there is a difference of more than 10% between the computed Lande g-factor and the Lande g-factor in pure LS-coupling. Finally, we compare the computed Lande g-factors with values from the Kurucz database.
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| 2. |
- Papoulia, Asimina
(författare)
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Computational Atomic Structure: Applications to Astrophysics and Nuclear Structure
- 2020
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with the modelling of atoms and ions. In heavy systems, where the effect of the nuclear size must be considered, a fully relativistic treatment based on the Dirac-Coulomb Hamiltonian is needed. Chapter two of the thesis provides an introduction to the basic principles of the fully relativistic multiconfiguration Dirac-Hartree-Fock (MCDHF) method, which is a variational approach for determining the wave functions. After we demonstrate how to obtain the best approximation of the wave functions by optimizing the energy expression, we describe how to compute the eigenvalues of operators other than the Hamiltonian, and how these eigenvalues correspond to measurable quantities. Chapter three and four, respectively, summarize the work done in the two published papers, illustrating some of the applications of the relativistic atomic structure theory.Paper I is an example of atomic structure calculations for astrophysical applications. Extensive amount of atomic transition data are produced for the systems of neutral and singly ionized aluminium that can be used to improve the interpretation of abundances in stars. Paper II demonstrates a novel method, in which the atomic structure calculations of isotope shifts are combined with experimental data, for extracting nuclear properties other than the charge radii.
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| 3. |
- Yordanov, Deyan T., et al.
(författare)
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Structural trends in atomic nuclei from laser spectroscopy of tin
- 2020
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Ingår i: Communications Physics. - : Springer Nature. - 2399-3650. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Tin is the chemical element with the largest number of stable isotopes. Its complete proton shell, comparable with the closed electron shells in the chemically inert noble gases, is not a mere precursor to extended stability; since the protons carry the nuclear charge, their spatial arrangement also drives the nuclear electromagnetism. We report high-precision measurements of the electromagnetic moments and isomeric differences in charge radii between the lowest 1/2(+), 3/2(+), and 11/2(-) states in Sn117-131, obtained by collinear laser spectroscopy. Supported by state-of-the-art atomic-structure calculations, the data accurately show a considerable attenuation of the quadrupole moments in the closed-shell tin isotopes relative to those of cadmium, with two protons less. Linear and quadratic mass-dependent trends are observed. While microscopic density functional theory explains the global behaviour of the measured quantities, interpretation of the local patterns demands higher-fidelity modelling. Measurements of the hyperfine structure of chemical elements isotopes provide unique insight into the atomic nucleus in a nuclear model-independent way. The authors present collinear laser spectroscopy data obtained at the CERN ISOLDE and measure hyperfine splitting along a long chain of odd-mass tin isotopes.
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