| 1. |
- Bengtsson, Peter, et al.
(author)
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Energy structure and transition rates in the Ne-like sequence from relativistic CI calculations
- 2012
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In: Europhysics Conference Abstracts;36C. - : European Physical Society. ; , s. 128-128
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Conference paper (other academic/artistic)abstract
- Atomic data are important in astrophysical applications and transition rates can be used in the determination of element abundances and plasma diagnostics. To provide for the extensive data needs a number of general computer codes such as SUPERSTRUCTURE, CIV3, and ATSP2K have been developed. As an alternative to these codes, which all rely on the Breit-Pauli approximation, the fully relativistic GRASP2K code can be used. GRASP2K is based on the multiconfiguration Dirac-Hartree-Fock method and implements a bi-orthogonal transformation method that permits initial and final states in a transition array to be optimized separately, which, in many cases, leads to more accurate values of the resulting rates. The GRASP2K package also contains modules to compute diagonal and off-diagonal hyperfine interaction constants, isotope shifts, Land´e gJ factors, and splittings of magnetic sub-state in intermediate and strong magnetic fields. In this work, GRASP2K has been applied to provide highly accurate spectroscopic data for ions in the Ne-like sequence between Mg III and Kr XXVII. Valence, core-valence, and core-core correlation effects were accounted for through SD-MR expansions to increasing sets of active orbitals. In Mg III, Al IV, Si V, P VI, S VII, and Ar IX, for which experimental energies are known to high accuracy, the mean error in the calculated energies is only 0.011%. For ions with no available experimental energy levels the calculated values should be most valuable in various applications. The high accuracy of the calculated energies makes it possible, in some cases, to to point out experimental values that are in error. Babushkin (length) and Coulomb (velocity) forms of transition rates are computed and agree to within a few percent for the majority of the allowed transitions. Computed lifetimes for states belonging to the 2p33s and 2p53d configurations are in good agreement with values from beam-foil measurements as well as from accurate MCHF Breit-Pauli calculations.
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| 2. |
- Ekman, Jörgen, et al.
(author)
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A spectral study of Te V from MCDHF calculations
- 2013
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In: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 46:9
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Journal article (peer-reviewed)abstract
- State-of-the-art multiconfiguration Dirac-Hartree-Fock calculations for Te V have been performed and energies, LS-compositions, radiative lifetimes and Lande gJ-factors for 51 odd and even parity states are presented. In addition, predictions on transition rates and oscillator strengths for a multitude of transitions between these states are reported for the first time. To describe the atomic system accurately, by means of configuration interaction, valence and core-valence electron correlation effects were taken into account. Calculated energies and lifetimes of excited states agree very well with experimental data.
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| 3. |
- Ekman, Jörgen, et al.
(author)
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Calculations with spectroscopic accuracy : energies, transition rates, and Landé g_J-factors in the carbon isoelectronic sequence from Ar XIII to Zn XXV
- 2014
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 564
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Journal article (peer-reviewed)abstract
- Extensive self-consistent multiconfiguration Dirac-Hartree-Fock (MCDHF) calculations and subsequent relativistic configuration in- teraction calculations are performed for 262 states belonging to the 15 configurations 2s22p2, 2s2p3, 2p4, 2s22p3l, 2s2p23l, 2p33l and 2s22p4l (l = 0,1,2) in selected carbon-like ions from Ar XIII to Zn XXV. Electron correlation effects are accounted for through large configuration state function expansions. Calculated energy levels are compared with existing theoretical calculations and data from the Chianti and NIST databases. In addition, Landé gJ -factors and radiative electric dipole transition rates are given for all ions. The accuracy of the calculations are high enough to facilitate the identification of observed spectral lines.
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| 4. |
- Ekman, Jörgen, et al.
(author)
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Large-scale calculations of atomic level and transition properties in the aluminum isoelectronic sequence from Ti X through Kr XXIV, Xe XLII, and W LXII
- 2018
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In: Atomic Data and Nuclear Data Tables. - : Elsevier. - 0092-640X .- 1090-2090. ; 120, s. 152-262
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Journal article (peer-reviewed)abstract
- Large-scale self-consistent multiconfiguration Dirac-Hartree-Fock subsequent relativistic configuration interaction (RCl) calculations are reported for 360 states belonging to the 30 configurations 3s(2))3l, 4l. 5l}, 3p(2) (3d, 4l}, 3s(3p(2). 3d(2)),3s{3p3d, 3p4l. 3p5s, 3d4l'}, 3p3d(2), 3p(3) and 3d(3) with I = 0, 1,, n - 1 and l' = 0. 1. 2 in 17 systems of the aluminum-like isoelectronic sequence: Ti X through Kr XXIV, Xe XLII, and W LXII. Effects from electron correlation are taken into account by means of large expansions in terms of a basis of configuration state functions (CSF) and calculated energy levels are compared with existing theoretical calculations and the NIST Atomic Spectra database. Radiative E1, E2, M1 and M2 transition rates and associated lifetimes of energy levels are presented in online tables. The uncertainties of the calculated energies are very small, on average between 0.02% and 0.05%, which aid new line identifications in laboratory and astronomical spectra and also make it possible to find and rule out misidentifications. The uncertainties of the El transition probabilities, based on the agreement between values in the length and velocity gauges, are estimated to be of the order 0.5% for the strong transitions and 25% for the weaker intercombination transitions. The M1 transition values are not sensitive to electron correlation and are believed to be accurate to well within 1%. (C) 2017 Published by Elsevier Inc.
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| 5. |
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| 6. |
- Ekman, Jörgen, et al.
(author)
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RIS4 : A program for relativistic isotope shift calculations
- 2019
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In: Computer Physics Communications. - : Elsevier. - 0010-4655 .- 1879-2944. ; 235, s. 433-446
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Journal article (peer-reviewed)abstract
- Spectral lines from different isotopes display a small separation in energy, commonly referred to as the line isotope shift. The program RIS4 (Relativistic Isotope Shift) calculates normal and specific mass shift parameters as well as field shift electronic factors from relativistic multiconfiguration Dirac-Hartree-Fock wave functions. These quantities, together with available nuclear data, determine isotope-dependent energy shifts. Using a reformulation of the field shift, it is possible to study, in a model-independent way, the atomic energy shifts arising from changes in nuclear charge distributions, e.g. deformations. (C) 2018 Published by Elsevier B.V.
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| 7. |
- Filippin, Livio, et al.
(author)
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Core correlation effects in multiconfiguration calculations of isotope shifts in Mg I
- 2016
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In: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : American Physical Society. - 2469-9926 .- 2469-9934. ; 93:6
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Journal article (peer-reviewed)abstract
- The present work reports results from systematic multiconfiguration Dirac-Hartree-Fock calculations of isotope shifts for several well-known transitions in neutral magnesium. Relativistic normal and specific mass shift factors as well as the electronic probability density at the origin are calculated. Combining these electronic quantities with available nuclear data, energy and transition level shifts are determined for the Mg26−Mg24 pair of isotopes. Different models for electron correlation are adopted. It is shown that, although valence and core-valence models provide accurate values for the isotope shifts, the inclusion of core-core excitations in the computational strategy significantly improves the accuracy of the transition energies and normal mass shift factors.
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| 8. |
- Filippin, Livio, et al.
(author)
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Multiconfiguration calculations of electronic isotope shift factors in Al I
- 2016
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In: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 94:6 : 062508
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Journal article (peer-reviewed)abstract
- The present work reports results from systematic multiconfiguration Dirac–Hartree–Fock calculations of electronic isotope shift factors for a set of transitions between low-lying levels of neutral aluminium. These electronic quantities together with observed isotope shifts between different pairs of isotopes provide the changes in mean-square charge radii of the atomic nuclei. Two computational approaches are adopted for the estimation of the mass- and field-shift factors. Within these approaches, different models for electron correlation are explored in a systematic way to determine a reliable computational strategy and to estimate theoretical error bars of the isotope shift factors.
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| 9. |
- Grumer, Jon, et al.
(author)
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Atomic Data and Stark Broadening Parameters for Sn II and Sn III
- 2013
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In: Book of abstracts. - : Institute of Modern Physics, Chinese Academy of Sciences.
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Conference paper (other academic/artistic)abstract
- Synopsis Extensive multicon guration Dirac-Hartree-Fock (MCDHF) and relativistic con guration interaction (RCI) calculations of energies, transition rates and broadening parameters are reported for Sn II and Sn III, ions which are of importance for plasma modeling. Results are compared with other recent works.
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| 10. |
- Jönsson, Per, et al.
(author)
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An Introduction to Relativistic Theory as Implemented in GRASP
- 2023
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In: Atoms. - : MDPI. - 2218-2004. ; 11:1
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Journal article (peer-reviewed)abstract
- Computational atomic physics continues to play a crucial role in both increasing the understanding of fundamental physics (e.g., quantum electrodynamics and correlation) and producing atomic data for interpreting observations from large-scale research facilities ranging from fusion reactors to high-power laser systems, space-based telescopes and isotope separators. A number of different computational methods, each with their own strengths and weaknesses, is available to meet these tasks. Here, we review the relativistic multiconfiguration method as it applies to the General Relativistic Atomic Structure Package [grasp2018, C. Froese Fischer, G. Gaigalas, P. Jonsson, J. Bieron, Comput. Phys. Commun. (2018). DOI: 10.1016/j.cpc.2018.10.032]. To illustrate the capacity of the package, examples of calculations of relevance for nuclear physics and astrophysics are presented.
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