| 21. |
- Jönsson, Per, et al.
(författare)
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Accurate Transition Probabilities from Large-Scale Multiconfiguration Calculations : a Tribute to Charlotte Froese Fischer
- 2013
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Ingår i: AIP Conference Proceedings. - : American Institute of Physics (AIP). - 0094-243X .- 1551-7616. ; 1545, s. 266-278
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Tidskriftsartikel (refereegranskat)abstract
- The development of multiconfiguration computer packages for atomic structure calculations is reviewed with special attention to the work of Charlotte Froese Fischer. The underlying theory is described along with methodologies to choose basis expansions of configuration state functions. Calculations of energies and transitions rates are presented and the accuracy of the results is assessed. Limitations of multiconfiguration methods are discussed and it is shown how these limitations can be circumvented by a division of the original large-scale computational problem into a number of smaller problems.
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| 22. |
- Jönsson, Per, et al.
(författare)
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An Introduction to Relativistic Theory as Implemented in GRASP
- 2023
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Ingår i: Atoms. - : MDPI. - 2218-2004. ; 11:1
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Tidskriftsartikel (refereegranskat)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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| 23. |
- Jönsson, Per, et al.
(författare)
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Atomic Structure Calculations with Spectroscopic Accuracy : Implications for Laboratory Work
- 2014
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Ingår i: Ninth International Conference on Atomic and Molecular Data and Their Applications: book of abstracts. ; , s. 112-112
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The observation of atomic spectra constitutes an important tool for diagnostics of astrophysical plasmas, and there is a boom of activity involving several new and planned multibillion-dollar telescopes. However, to correctly interpret observed spectra, the atomic lines must be known and identified from laboratory work. Laboratory work is hard and time-consuming, and present efforts do not in any way match the needs for data, partly due to lack of funding [1] and partly due to experimental limitations. One goal of atomic structure calculations is to provide energy differences with ”spectroscopic accuracy” to aid laboratory work. Using highly accurate calculated energy differences it should be possible to directly validate or rule out experimental energy level and line identifications. New and efficient methods for solving the Dirac-equation for many electron systems, together with today’s fast computers, indeed make it possible to perform calculations with spectroscopic accuracy for ions of medium complexity. We give a number of examples of calculations based on the relativistic configuration interaction (RCI) method in B-, C-, N-, O-, and Ne-like systems, where energies levels far up in the spectrum have been predicted with uncertainties of 0.05 % or less [2,3,4]. Depending on the spectral range, these uncertainties are in many cases close to what can be experimentally obtained. The above mentioned calculations reveal that many experimental energy levels given in the literature and in data bases are wrong and based on misidentifications. We finally show how the accuracy of atomic structure calculations can be further improved, and results extended to more complex systems, by using the novel partitioned configuration function interaction (PCFI) method [5]. Some practical consequences of the recent advances in computational methodology for laboratory work are discussed.
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| 24. |
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| 25. |
- Jönsson, Per, et al.
(författare)
-
Energies, Transition Rates, Hyperfine Structures, and Landé gJ Factors for the Fine-structure Levels of the 2s22p2, 2s2p3, and 2p4 Configurations in Carbon-like Ions between F IV and Ni XXIII
- 2011
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Ingår i: Atomic Data and Nuclear Data Tables. - : Elsevier. - 0092-640X .- 1090-2090. ; 97:6, s. 648-691
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Tidskriftsartikel (refereegranskat)abstract
- Energies, electric dipole, magnetic dipole, and electric quadrupole transition rates, hyperfine structures, and Landé g J factors from relativistic configuration interaction calculations are reported for the states of the (1s 2 )2s 2 2p 2 , 2s2p 3 , and 2p 4 configurations in all carbon-like ions between F IV and Ni XXIII. Valence, core-valence, and core-core correlation effects were accounted for through single/double-excitation-multireference expansions to increasing sets of active orbitals. The calculated energy levels generally agree within a few hundred cm -1 with the experimentally compiled results, and the Babushkin (length), and Coulomb (velocity) forms of transition rates agree within less than 1% for a majority of the allowed transitions.
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| 26. |
- Jönsson, Per, et al.
(författare)
-
Energy levels and transition rates for the boron isoelectronic sequence : Si X, Ti XVIII – Cu XXV
- 2013
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 559
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Tidskriftsartikel (refereegranskat)abstract
- Relativistic configuration interaction (RCI) calculations are performed for 291 states belonging to the configurations 1s22s22p, 1s22s2p2, 1s22p3, 1s22s23l, 1s22s2p3l, 1s22p23l, 1s22s24l , 1s22s2p4l , and 1s22p24l (l = 0, 1,2 and l = 0, 1, 2, 3) in boron-like ions Si X and Ti XVIII to Cu XXV. Electron correlation effects are represented in the wave functions by large configuration state function (CSF) expansions. States are transformed from j j-coupling to LS -coupling, and the LS -percentage compositions are used for labeling the levels. Radiative electric dipole transition rates are given for all ions, leading to massive data sets. Calculated energy levels are compared with other theoretical predictions and crosschecked against the Chianti database, NIST recommended values, and other observations. The accuracy of the calculations are high enough to facilitate the identification of observed spectral lines.
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| 27. |
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| 28. |
- Jönsson, Per, et al.
(författare)
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GRASP Manual for Users
- 2023
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Ingår i: Atoms. - : MDPI. - 2218-2004. ; 11:4
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Tidskriftsartikel (refereegranskat)abstract
- grasp is a software package in Fortran 95, adapted to run in parallel under MPI, for research in atomic physics. The basic premise is that, given a wave function, any observed atomic property can be computed. Thus, the first step is always to determine a wave function. Different properties challenge the accuracy of the wave function in different ways. This software is distributed under the MIT Licence.
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| 29. |
- Jönsson, Per, et al.
(författare)
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Hyperfine structures, isotope shifts and transition rates of C II, N III, and O IV from relativistic configuration interaction calculations
- 2010
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Ingår i: Atomic Data and Nuclear Data Tables. - : Elsevier. - 0092-640X .- 1090-2090. ; 96:3, s. 271-298
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Tidskriftsartikel (refereegranskat)abstract
- Energy levels, specific mass shift parameters, hyperfine interaction constants, Landé gJ factors, and transition probabilities between computed levels are reported for C II, N III, and O IV. Results include levels belonging to 2s22p,2s2p2,2p3,2s23s,2s23p,2s23d,2s2p3s and, in the case of C II, the 2s24s and 2s24p configurations. Wavefunctions were determined using the multiconfiguration Dirac–Hartree–Fock method and account for valence, core–valence, and core–core correlation effects.
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| 30. |
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