| 1. |
- 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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| 2. |
- Gaigalas, Gediminas, et al.
(författare)
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Energy level structure of Er3+ free ion and Er3+ ion in Er2O3 crystal
- 2014
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Ingår i: National Institute for Fusion Science, Research Report NIFS-DATA. - : National Institute for Fusion Science. - 0915-6364. ; :115, s. 1-25
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The latest version of the GRASP2K atomic structure package [P. J¨onsson, G. Gaigalas, J. Biero´n, C. Froese Fischer, I.P. Grant, Comput. Phys. Commun. 184 (2013) 2197], based on the multiconfigurational Dirac-Hartree-Fock method, is extended to account for effects of crystal fields in complex systems. Energies from relativistic configuration interaction calculations are reported for the Er3+ free ion. E2 and M1 line strengths, weighted oscillator strengths, and rates are presented for transitions between states of the [Xe]4f11 configuration. Also Stark levels of the Er3+ 4Io 15/2 state in Er2O3 are calculated in the ab initio point charge crystal field approximation. In all calculations the Breit interaction and leading QED effects are included as perturbations. Different strategies for describing electron correlation effects are tested and evaluated. The final results are compared with experiment and other methods.
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| 3. |
- 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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| 4. |
- 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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| 5. |
- Jönsson, Per, et al.
(författare)
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The Computational Atomic Structure Group : Code Development and Available Resources
- 2014
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Ingår i: Ninth International Conference on Atomic and Molecular Data and Their Applications: book of abstracts. ; , s. 113-113
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- There is an increasing demand for accurate atomic data due to advancements in experimental techniques and investments in large scale research facilities. In astrophysics the quality and resolution of solar and stellar spectra has so improved that the accuracy of atomic data is frequently a limiting factor in the interpretation. Accurate atomic data are also required in plasma physics and in other emerging areas such as laser spectroscopy on isotope separators, X-ray lithography, and lighting research. The needs include accurate transition energies, fine- and hyperfine structures, mass- and field shifts as well as parameters related to interaction with external magnetic fields. Also there is a constant need for transition rates of different multipolarities between excited states. Data are needed for a wide range of elements and ionization stages. To meet the demands for accurate atomic data the COMPutational Atomic Structure (COMPAS) group has been formed. The group is involved in developing state of the art computer codes for atomic structure calculations in the non-relativistic scheme with relativistic corrections in the Breit-Pauli approximation [1] as well as in the fully relativistic domain. Here we describe new developments of the GRASP2K relativistic atomic structure code [2,3]. We present results for a number of systems and properties to illustrate the potential and restriction of modern computational atomic structure. Among the properties are transition rates, hyperfine- and magnetically induced rates, energy structure, and isotope shifts. We also discuss current code developments and plans for future work. The codes developed by the COMPAS group, along with detailed user manuals, are freely available at http://ddwap.mah.se/tsjoek/compas/ .
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| 6. |
- Naze, Cedric, et al.
(författare)
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Isotope Shifts in Beryllium-, Boron-, Carbon-, and Nitrogen-like Ions from Relativistic Configuration Interaction Calculations
- 2014
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Ingår i: Atomic Data and Nuclear Data Tables. - : Elsevier. - 0092-640X .- 1090-2090. ; 100:5, s. 1197-1249
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Tidskriftsartikel (refereegranskat)abstract
- Energy levels, normal and specific mass shift parameters as well as electronic densities at the nucleus are reported for numerous states along the beryllium, boron, carbon, and nitrogen isoelectronic sequences. Combined with nuclear data, these electronic parameters can be used to determine values of level and transition isotope shifts. The calculation of the electronic parameters is done using first-order perturbation theory with relativistic configuration interaction wavefunctions that account for valence, core–valence, and core–core correlation effects as zero-order functions. Results are compared with experimental and other theoretical values, when available.
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| 7. |
- Radziute, Laima, et al.
(författare)
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Energy level structure of Er3
- 2014
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier. - 0022-4073 .- 1879-1352. ; 152, s. 94-106
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Tidskriftsartikel (refereegranskat)abstract
- AtomicenergylevelsandE2andM1transitionratesarereportedforthe[Xe]4f11 ground configurationinEr3þ from relativisticmulticonfigurationDirac–Hartree–Fockandcon- figuration interactioncalculations.TheBreittransverseinteractionandleadingQED effectsareincludedasperturbations.Differentstrategiesfordescribingelectroncorrela- tion effectsaretestedandevaluated.Thecalculatedenergylevelsarecomparedwith experimentandresultsfromsemi-empiricalmethods.
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| 8. |
- Radziute, Laima, et al.
(författare)
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Energy level structure of Er3+ free ion
- 2014
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Ingår i: Ninth International Conference on Atomic and Molecular Data and Their Applications: book of abstracts. ; , s. 91-91
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Ab initio calculations for the Er3+ ion are performed using GRASP2K package, based on multiconfigurational Dirac-Hartree-Fock method (MCDHF). 41 energy levels of the [Xe]4f 11 con- figuration are calculated. The study includes different types of correlations using different strategies. The Breit interaction and leading QED effects are included as perturbations in all calculations. We present the results of the 10 lowest levels (see Table 1), obtained by single and double excitations corresponding to valence, core, and core-valence correlations. Levels are notated in the form (2S+1)L Nr J , where instead of the group labels νW U, single character ”numbers” Nr are used. Deviation of our values for energy levels from NIST database reaches 6.9%. Energy levels given at NIST are derived from the spectrum of Er3+ in LaF3 [1].
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| 9. |
- Radziute, Laima, et al.
(författare)
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Multiconfiguration Dirac-Hartree-Fock calculations of atomic electric dipole moments of 225Ra, 199Hg, and 171Yb
- 2014
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 90
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Tidskriftsartikel (refereegranskat)abstract
- The multiconfiguration Dirac-Hartree-Fock method is employed to calculate atomic electric dipole moments in the ground states of 225Ra, 199Hg, and 171Yb. For the calculations of the matrix elements we extend the relativistic atomic structure package GRASP2K. The extension includes programs to evaluate matrix elements of PT -odd electron-nucleus tensor-pseudotensor and pseudoscalar-scalar interactions, the atomic electric dipole operator, the nuclear Schiff moment, and the interaction of the electron electric dipole moment with nuclear magnetic moments. The interelectronic interactions are accounted for through valence and core-valence electron correlation effects. The electron shell relaxation is included with separately optimized wave functions of opposite parities.
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| 10. |
- Rynkun, Pavel, et al.
(författare)
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Energies and E1, M1, E2, and M2 transition rates for states of the 2s22p3, 2s2p4, and 2p5 configurations in nitrogen-like ions between F III and Kr XXX
- 2014
-
Ingår i: Atomic Data and Nuclear Data Tables. - : Elsevier. - 0092-640X .- 1090-2090. ; 100:2, s. 315-402
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Tidskriftsartikel (refereegranskat)abstract
- Based on relativistic wavefunctions from multiconfiguration Dirac–Hartree–Fock and configuration interaction calculations, E1, M1, E2, and M2 transition rates, weighted oscillator strengths, and lifetimes are evaluated for the states of the (1s2)2s22p3, 2s2p4, and 2p5 configurations in all nitrogen-like ions between F III and Kr XXX. The wavefunction expansions include valence, core–valence, and core–core correlation effects through single–double multireference expansions to increasing sets of active orbitals. The computed energies agree very well with experimental values, with differences of only 300–600 cm−1 for the majority of the levels and ions in the sequence. Computed transitions rates are in close agreement with available data from MCHF-BP calculations by Tachiev and Froese Fischer [G.I. Tachiev, C. Froese Fischer, A&A 385 (2002) 716].
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