| 1. |
- Gaidamauskas, Erikas, et al.
(author)
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Tensorial form and matrix elements of the relativistic nuclear recoil operator
- 2011
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In: Journal of Physics B. - : IOP Publishing Ltd. - 0953-4075 .- 1361-6455. ; 44:17
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Journal article (peer-reviewed)abstract
- Within the lowest-order relativistic approximation (∼v2/c2) and to first order in me/M, the tensorial form of the relativistic corrections of the nuclear recoil Hamiltonian is derived, opening interesting perspectives for calculating isotope shifts in the multiconfiguration Dirac–Hartree–Fock framework. Their calculation is illustrated for selected Li-, B- and C-like ions. This work underlines the fact that the relativistic corrections to the nuclear recoil are definitively necessary for obtaining reliable isotope shift values.
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| 2. |
- Jönsson, Per, et al.
(author)
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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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In: Atomic Data and Nuclear Data Tables. - : Elsevier. - 0092-640X .- 1090-2090. ; 97:6, s. 648-691
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Journal article (peer-reviewed)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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| 3. |
- Jönsson, Per, et al.
(author)
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Transition rates in the B-, C-, N-, O-, and Ne-like sequences from relativistic CI calculations
- 2011
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In: Abstracts 43rd Conference of the European Group for Atomic Systems (EGAS). - : European Physical Society. ; , s. 142-142
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Conference paper (other academic/artistic)abstract
- Atomic data are important in astrophysical applications and transition data can be used in the determination of element abundances and plasma diagnostics [1]. 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 [2] can be used. GRASP2K is based on the multicon guration Dirac-Hartree-Fock method and implements a bi-orthogonal transformation method that permits initial and nal states in a transition array to be optimized separately, which, in many cases, leads to more accurate values of the resulting rates [3]. The GRASP2K package also contains modules to compute diagonal and o -diagonal hyper ne interaction constants, isotope shifts, Land e gJ factors, and splittings of magnetic sub-state in intermediate and strong magnetic elds. In this work, GRASP2K has been applied to provide highly accurate spectroscopic data for transitions in the B-, C-, N-, O-, and Ne-like sequences [4]. Valence, core-valence, and core-core correlation e ects were accounted for through SD-MR expansions to increasing sets of active orbitals. The calculated energy levels generally agree to within a few hundred cm with the experimentally compiled results. Babushkin (length) and Coulomb (velocity) forms of transition rates di er with less than 1% for the majority of the allowed transitions. The perspectives of massive data production on parallel clusters to cover the needs of the astrophysical community is discussed.
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| 4. |
- Verdebout, Simon, et al.
(author)
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Interaction of Variational Localized Correlation Functions for Atomic Properties
- 2011
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In: Abstracts 43rd Conference of the European Group for Atomic Systems (EGAS). - : European Physical Society. ; , s. 155-155
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Conference paper (other academic/artistic)abstract
- Variational methods are used for targeting speci c correlation e ects by tailoring the con- guration space. Independent sets of correlation orbitals, embedded in the localized correlation functions (LCFs), are produced from the multicon guration Hartree-Fock (MCHF) or Dirac- Hartree-Fock (MCDHF) calculations [1,2]. These non-orthogonal functions are then coupled to each other by solving the associated generalized eigenproblem. The Hamiltonian and overlap matrix elements are evaluated using the biorthonormal orbital transformations and e cient counter-transformations of the con guration interaction eigenvectors [3]. This method was successfully applied for describing the total energy of the ground state of beryllium [4]. Moreover it has been shown that the energy convergence is faster than with the usual SD-MCHF method for which a single set of orthonormal one-electron orbitals spanning the complete con guration space is optimized. In the present work, we investigate the interaction of localized correlation functions (LCFI), not only for the 1s22s2 1S state of beryllium but also for the rst two excited states: 1s22s2p 3Po and 1s22s2p 1Po. For these three states, we evaluate the total energy but also the expectation values of the speci c mass shift (SMS) operator, the hyper ne structure (HFS) parameters and the transition probabilities. The comparison between the SMS and HFS results obtained using the LCFI method and the traditional MCHF one stresses the importance of the mixing coe cients contraction within each LCF function. We demonstrate that this unwanted contraction e ect can be bypassed by enlarging the associated generalized eigenproblem. The beryllium atom is a system for which it is still possible to saturate a single orthonormal orbital set through the complete active space MCHF expansions. As such, it constitutes the perfect benchmark for the LCFI method. For larger systems, it becomes hopeless to saturate a single common set of orthonormal orbitals, the LCFI method should be a good alternative for reaching a full-correlated wave function. The present study is a rst step in the current development of the extension of both ATSP2K and GRASP2K packages [1,2] that will adopt the biorthonormal treatment for energies, isotope shifts, hyper ne structures and transition probabilities.
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| 5. |
- Verdebout, Simon, et al.
(author)
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Interaction of Variational Localized Correlation Functions for Atomic Properties of Be I
- 2011
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Conference paper (other academic/artistic)abstract
- We present some progress associated to the localised correlation function interaction (LCFI) method. In this report, the LCFI method is tested not only for total energy but also for the speci c mass shift operator, the hyper ne structure parameters and the transition probabilities. These properties are computed for the three lowest electronic states of the beryllium atom. These calculations illustrate the importance of the contraction e ects.
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