| 1. |
- Bengtsson, Peter, et al.
(författare)
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Energy structure and transition rates in the Ne-like sequence from relativistic CI calculations
- 2012
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Ingår i: Europhysics Conference Abstracts;36C. - : European Physical Society. ; , s. 128-128
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)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.
(författare)
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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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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 564
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Tidskriftsartikel (refereegranskat)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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| 3. |
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| 4. |
- 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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| 5. |
- 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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| 6. |
- Jönsson, Per, et al.
(författare)
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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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| 7. |
- 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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| 8. |
- Jönsson, Per, et al.
(författare)
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Multiconfiguration Dirac-Hartree-Fock Calculations with Spectroscopic Accuracy : Applications to Astrophysics
- 2017
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Ingår i: Atoms. - : MDPI. - 2218-2004. ; 5:2
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Forskningsöversikt (refereegranskat)abstract
- Atomic data, such as wavelengths, spectroscopic labels, broadening parameters and transition rates, are necessary for many applications, especially in plasma diagnostics, and for interpreting the spectra of distant astrophysical objects. The experiment with its limited resources is unlikely to ever be able to provide a complete dataset on any atomic system. Instead, the bulk of the data must be calculated. Based on fundamental principles and well-justified approximations, theoretical atomic physics derives and implements algorithms and computational procedures that yield the desired data. We review progress and recent developments in fully-relativistic multiconfiguration Dirac-Hartree-Fock methods and show how large-scale calculations can give transition energies of spectroscopic accuracy, i.e., with an accuracy comparable to the one obtained from observations, as well as transition rates with estimated uncertainties of a few percent for a broad range of ions. Finally, we discuss further developments and challenges.
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| 9. |
- Jönsson, Per, et al.
(författare)
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Relativistic CI Calculations of Spectroscopic Data for the 2p(6) and 2p(5)3l Configurations in Ne-lika Ions between Mg III and Kr XXVII
- 2011
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Energies, E1, M1, E2, M2 transition rates, oscillator strengths, and lifetimes from relativistic configuration interaction calculations are reported for the states of the 2p6, 2p53s, 2p53p, and 2p53d, configurations in all Ne-like ions between Mg III and Kr XXVII. Core-valence and core-core correlation effects are accounted for through SD-expansions to increasing sets of active orbitals. The Breit interaction and leading QED effects are included as perturbations. The results are compared with experiments and other recent benchmark calculations. 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%.
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| 10. |
- Jönsson, Per, et al.
(författare)
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Relativistic CI calculations of spectroscopic data for the 2p6 and 2p53l configurations in Ne-like ions between Mg III and Kr XXVII
- 2014
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Ingår i: Atomic Data and Nuclear Data Tables. - : Elsevier. - 0092-640X .- 1090-2090. ; 100:1, s. 1-154
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Tidskriftsartikel (refereegranskat)abstract
- Energies, E1, M1, E2, M2 transition rates, oscillator strengths, and lifetimes from relativistic configuration interaction calculations are reported for the states of the 2p6, 2p53s, 2p53p, and 2p53d, configurations in all Ne-like ions between Mg III and Kr XXVII. Core–valence and core–core correlation effects are accounted for through single and double excitations to increasing sets of active orbitals. The Breit interaction and leading quantum electrodynamic effects are included as perturbations. The results are compared with experiments and other recent benchmark calculations. 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%.
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