| 1. |
- Bieron, Jacek, et al.
(författare)
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Ab initio MCDHF calculations of electron-nucleus interactions
- 2015
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Ingår i: Physica Scripta. - : Institute of Physics Publishing (IOPP). - 0031-8949 .- 1402-4896. ; 90:5
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Tidskriftsartikel (refereegranskat)abstract
- We present recent advances in the development of atomic ab initio multiconfiguration Dirac– Hartree–Fock theory, implemented in the GRASP relativistic atomic structure code. For neutral atoms, the deviations of properties calculated within the Dirac–Hartree–Fock (DHF) method (based on independent particle model of an atomic cloud) are usually dominated by electron correlation effects, i.e. the non-central interactions of individual electrons. We present the recent advances in accurate calculations of electron correlation effects in small, medium, and heavy neutral atoms. We describe methods of systematic development of multiconfiguration expansions leading to systematic, controlled improvement of the accuracy of the ab initio calculations. These methods originate from the concept of the complete active space (CAS) model within the DHF theory, which, at least in principle, permits fully relativistic calculations with full account of electron correlation effects. The calculations within the CAS model on currently available computer systems are feasible only for very light systems. For heavier atoms or ions with more than a few electrons, restrictions have to be imposed on the multiconfiguration expansions. We present methods and tools, which are designed to extend the numerical calculations in a controlled manner, where multiconfiguration expansions account for all leading electron correlation effects. We show examples of applications of the GRASP code to calculations of hyperfine structure constants, but the code may be used for calculations of arbitrary bound-state atomic properties. In recent years it has been applied to calculations of atomic and ionic spectra (transition energies and rates), to determinations of nuclear electromagnetic moments, as well as to calculations related to interactions of bound electrons with nuclear electromagnetic moments leading to violations of discrete symmetries.
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| 2. |
- Radziute, Laima, et al.
(författare)
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Energy level structure of the ground configuration in the Er3+ free ion
- 2015
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Ingår i: Physica Scripta. - : Bibliopolis, Edizioni di Filosofia e Scienze. - 0031-8949 .- 1402-4896. ; 90:5
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Tidskriftsartikel (refereegranskat)abstract
- Energy levels of the ground configuration [Xe]4f11 in the Er3+ ion are reported from relativistic configuration interaction calculations. Calculations are performed using the relativistic atomic structure package GRASP2K, which implements the multiconfiguration Dirac–Hartree–Fock method. The Breit transverse interaction and leading QED effects are included as perturbations. The final energies of 41 levels are compared with results from experiment and semi-empirical methods.
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| 3. |
- Radziute, Laima, et al.
(författare)
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Extended calculations of level and transition properties in the nitrogen isoelectronic sequence : Cr XVIII, Fe XX, Ni XXII, and Zn XXIV
- 2015
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 582
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Tidskriftsartikel (refereegranskat)abstract
- Extensive multiconfiguration Dirac-Hartree-Fock (MCDHF) calculations and relativistic configuration interaction (RCI) calculations are performed for 272 states of the 2s22p3, 2s2p4, 2p5, 2s22p23l, 2s2p33l, and 2p43l (l = 0, 1, 2) configurations in the nitrogen-like ions Cr XVIII, Fe XX, Ni XXII, and Zn XXIV. Valence, core-valence, and core-core electron correlation effects are accounted for through large configuration state function expansions. Calculated energy levels are compared with data from other calculations and with experimental data from the NIST database. Landé gJ -factors; hyperfine structures; isotope shifts; and radiative electric dipole (E1), electric quadrupole (E2), and magnetic dipole (M1) transition rates are given for all ions. The accuracy of the calculated energy levels is high enough to facilitate identification of observed spectral lines involving the 2l43l configurations, for which experimental data
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| 4. |
- Radziute, Laima, et al.
(författare)
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Weak- and hyperfine-interaction-induced 1s2s 1S0-1s2 1S0 E1 transition rates of He-like ions
- 2015
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Ingår i: Chinese Physics B. - : Institute of Physics Publishing (IOPP). - 1674-1056. ; 24:4
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Tidskriftsartikel (refereegranskat)abstract
- Weak- and hyperfine-interaction-induced 1s2s 1S0 -1s2 1S0 E1 transition rates for the isoelectronic sequence of He-like ions have been calculated using the multiconfiguration Dirac–Hartree–Fock (MCDHF) and relativistic configuration interaction methods. The results should be helpful for the future experimental investigations of parity non-conservation effects.
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