| 1. |
- Froese Fischer, Charlotte, et al.
(författare)
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Configuration interaction with separately optimized pair correlation functions
- 2010
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Variational methods produce one-electron radial functions that minimize the total energy of the system. Independent pair correlation functions (PCFs) designed to represent a specific correlation effect – valence, core-valence, or core-core – can be obtained from multiconfiguration Hartree-Fock (MCHF) or Dirac-Hartree-Fock (MCDHF) calculations [1,2]. These separately optimized and nonorthogonal PCFs may then be coupled by solving the associated generalized eigenproblem. In the present study, the Hamiltonian and overlap matrix elements are evaluated through biorthonormal orbital transformations and efficient counter-transformation of the configuration interaction eigenvectors [3]. The ground state of Be atom has been thoroughly tested by this method for various computational strategies and correlation models. It has been shown that the energy convergence is faster than with the usual SD-MCHF method of optimizing a single, orthonormal, one-electron orbital basis spanning the complete configuration space. Beryllium is a small system for which basis saturation can be achieved through complete active space MCHF expansions. But for larger systems describing electron correlation in all space by optimizing a common orthonormal set becomes hopeless whereas the calculation of additional PCFs is straight forward. Our independent optimization scheme, raises many questions related in the choice of the zero-order model to be used when building the interaction matrix. The present study is the first step in the current development of the extension of the atsp2K and grasp2K packages [1,2] that will adopt the biorthonormal treatment for energies, isotope shifts, hyperfine structures and transition probabilities.
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| 2. |
- Froese Fischer, Charlotte, et al.
(författare)
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Doublet-quartet energy separation in boron : a partitioned-correlationfunction- interaction method
- 2013
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 88:6
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Tidskriftsartikel (refereegranskat)abstract
- No lines have been observed for transitions between the doublet and quartet levels of B I. Consequently, energy levels based on observation for the latter are obtained through extrapolation of wavelengths along the isoelectronic sequence for the 2s22p 2Po 3/2 – 2s2p2 4P5/2 transition. In this paper, accurate theoretical excitation energies from a partitioned-correlation-function-interaction (PCFI) method are reported for B I that include both relativistic effects in the Breit-Pauli approximation and a finite mass correction. Results are compared with extrapolated values from observed data. For B I our estimate of the excitation energy 28 959 ± 5 cm−1 is in better agreement with the values obtained by Edl´en et al. (1969) than those reported by Kramida and Ryabtsev (2007). Our method is validated by applying the same procedure to the separation of these levels in C II.
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| 3. |
- Grumer, Jon, et al.
(författare)
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Atomic Data and Stark Broadening Parameters for Sn II and Sn III
- 2013
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Ingår i: Book of abstracts. - : Institute of Modern Physics, Chinese Academy of Sciences.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Synopsis Extensive multicon guration Dirac-Hartree-Fock (MCDHF) and relativistic con guration interaction (RCI) calculations of energies, transition rates and broadening parameters are reported for Sn II and Sn III, ions which are of importance for plasma modeling. Results are compared with other recent works.
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| 4. |
- Jönsson, Per, et al.
(författare)
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Spectral properties of Sb IV from MCDHF calculations
- 2012
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Ingår i: Journal of Physics B. - : Bibliopolis, Edizioni di Filosofia e Scienze. - 0953-4075 .- 1361-6455. ; 45:16
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Tidskriftsartikel (refereegranskat)abstract
- We report on extensive relativistic multiconfiguration Dirac–Hartree–Fock (MCDHF) spectrum calculations for Sb IV. Energies, LS-compositions and Landé gJ-factors for 60 odd- and even-parity states are computed along with lifetimes and rates for transitions between these states. Results for the 5s2 1S0–5s5p 3Po0 hyperfine-induced transition are also presented. Valence and core-valence electron correlation effects are accounted for by explicit configuration interaction. The calculated energies agree very well with experiment, but the labelling of some of the odd states is ambiguous due to close degeneracies between the 5p5d, 5s7p and 5p6s configurations. Computed lifetimes of the excited states are compared with values from cascade-corrected beam-foil measurements.
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| 5. |
- Naze, Cedric, et al.
(författare)
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Isotope shift parameters, hyperfine interaction constants and Landte factors along the Be, B, C and N isoelectronic sequences
- 2012
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Ingår i: Europhysics Conference Abstracts;36C. - : European Physical Society. ; , s. 143-143
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The mass shift parameters, the electron density at the origin, the hyperfine interaction constants and the gJ Land´e factors are computed along the beryllium, boron, carbon and nitrogen isoelectronic sequences. The calculations on B- and C-like ions are based on the wave functions described in [1-4]. The many-electron wave functions corresponding to the Be and N isoelectronic sequences are obtained using the new version of the grasp2K multiconfiguration Dirac-Fock package, following similar optimization strategies. A new program, hereafter referred as ris and designed as a module of grasp2K, calculates the mass shift parameters and the electron density at the origin within the relativistic framework. For estimating the mass shift, ris considers the expectation value of the following operator HMS = 1 2M N Xi , j pi · pj − αZ ri i + ( i · ri) ri r2 i · pj , that is more complete than the one calculated in sms92. The one-body part (i = j) of the first term of equation is responsible for the observed breakdown of the Dirac kinetic energy operator often used to evaluate the isotope normal mass shift. The second term of equation takes the nuclear recoil corrections into account at the (αZ) order. The programs ris and rhfs2 allow the storage of the angular coefficients to reduce the cpu time when calculations are performed along a given isoelectronic sequence.
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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. |
- Petryla, Andrius, et al.
(författare)
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Theoretical and experimental studies of In I, Sn II, Sb III, and Te IV atomic properties
- 2012
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Ingår i: Europhysics Conference Abstracts;36C. - : European Physical Society. ; , s. 42-42
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We use relativistic multiconfiguration Dirac-Hartree-Fock and configuration interaction calculations to study 5s2nl and 5s5p2 configurations of In I, Sn II, Sb III, and Te IV. Energies, transition amplitudes, Land´e gJ-factors, and hyperfine constants are calculated using a correlation model that accounts for valence and core-valence correlation. Also spin- and orbital polarization effects are accounted for by single excitations from all core-shells to an increasing set of active orbitals. Transformed to the LSJ-coupling scheme, using the new features of the GRASP2K program, the calculated wave functions shed light on the difficulties in labeling some states due to the extensive 5s25d and 5s5p2 configuration interaction. Our results are compared with experimental values and values from relativistic many-body perturbation theory (RMBPT) and all-order single-double (SD) calculations. The theoretical work is complemented with experiment, and new hyperfine interaction constants are derived for several states in In I from high resolution Fourier Transform Spectra.
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| 8. |
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| 9. |
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| 10. |
- Verdebout, Simon, et al.
(författare)
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A Partitioned Correlation Function Approach for Atomic Properties (Washington)
- 2012
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Ingår i: Program and Abstracts. ; , s. 118-118
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Variational methods are used for targeting specific correlation effects by tailoring the configuration space. Independent sets of correlation orbitals, embedded in partitioned correlation functions (PCFs), are produced from multiconfiguration Hartree-Fock (MCHF) and DiracHartree-Fock (MCDHF) calculations. These non-orthogonal functions span configuration state function (CSF) spaces that are coupled to each other by solving the associated generalized eigenvalue problem. The Hamiltonian and overlap matrix elements are evaluated using the biorthonormal orbital transformations and efficient counter-transformations of the configuration interaction eigenvectors [1]. This method was successfully applied for describing the total energy of the ground state of beryllium [2]. Using this approach, we demonstrated the fast energy convergence in comparison with the conventional SD-MCHF method optimizing a single set of orthonormal one-electron orbitals for the complete configuration space. In the present work, we investigate the Partitioned Correlation Function Interaction (PCFI) approach for the two lowest states of neutral lithium, i.e. 1s 2 2s 2 S and 1s 2 2p 2 P o . For both states, we evaluate the total energy, as well as the expectation values of the specific mass shift operator, the hyperfine structure parameters and the transition probabilities using different models for tailoring the configuration space. We quantify the “constraint effect” due to the use of fixed PCF eigenvector compositions and illustrate the possibility of a progressive deconstraint, up to the non-orthogonal configuration interaction limit case. The PCFI estimation of the position of the quartet system relative to the ground state of B I will also be presented. The PCFI method leads to an impressive improvement in the convergence pattern of all the spectroscopic properties. As such, Li I, Be I and B I constitute perfect benchmarks for the PCFI method. For larger systems, it becomes hopeless to saturate a single common set of orthonormal orbitals and the PCFI method is a promising approach for getting high quality correlated wave functions. The present study constitutes a major step in the current developments of both atsp2K and grasp2K packages that adopt the biorthonormal treatment for estimating energies, isotope shifts, hyperfine structures and transition probabilities.
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