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Research paper thumbnail of Weak correlation and strong relativistic effects on the hyperfine interaction in fluorine

Physical Review A

In previous work devoted to ab initio calculations of hyperfine structure constants in nitrogen a... more In previous work devoted to ab initio calculations of hyperfine structure constants in nitrogen and fluorine atoms, we observed sizeable relativistic effects, a priori unexpected for such light systems, that can even largely dominate over electron correlation. We observed that the atomic wave functions calculated in the Breit-Pauli approximation describe adequately the relevant atomic levels and hyperfine structures, even in cases for which a small relativistic LS-term mixing becomes crucial. In the present work we identify new levels belonging to the spectroscopic terms 2p 4 (3 P)3d 2,4 (P, D, F) of the fluorine atom, for which correlation effects on the hyperfine structures are small, but relativistic LS-term admixtures are decisive to correctly reproduce the experimental values. The Breit-Pauli analysis of the hyperfine matrix elements nails cases with large cancellation, either between LS pairs for individual hyperfine operators, or between the orbital and the spin-dipole contributions. Multiconfiguration Dirac-Hartree-Fock calculations are performed to support the Breit-Pauli analysis.

Research paper thumbnail of Theoretical hyperfine structures of F19 i and O17 i

Physical Review A, 2018

Multiconfiguration Hartree-Fock (MCHF) and multiconfiguration Dirac-Hartree-Fock (MCDHF) calculat... more Multiconfiguration Hartree-Fock (MCHF) and multiconfiguration Dirac-Hartree-Fock (MCDHF) calculations are performed for the 2p 5 2 P o , 2p 4 (3 P)3s 4 P , 2p 4 (3 P)3s 2 P and 2p 4 (3 P)3p 4 S o states of 19 F I to determine their hyperfine constants. Several computing strategies are considered to investigate electron correlation and relativistic effects. High-order correlation contributions are included in MCHF calculations based on single and double multireference (SD-MR) expansions. The largest components of the single reference MCHF wave functions are selected to define the MR sets. In this scheme, relativistic corrections are evaluated in the Breit-Pauli approximation. A similar strategy is used for the calculation of MCDHF relativistic wave functions and hyperfine parameters. While correlation and relativistic corrections are found to be rather small for the ground state, we highlight large relativistic effects on the hyperfine constant A 3/2 of 2p 4 (3 P)3p 4 S o and, to a lesser extent, on A 1/2 of 2p 4 (3 P)3s 4 P. As expected for such a light system, electron correlation effects dominate over relativity in the calculation of the hyperfine interaction of all other levels considered. We also revisit the hyperfine constants of 2p 3 (4 S)3s 5 S o and 2p 3 (4 S)3p 5 P in 17 O using similar strategies. The results are found to be in excellent agreement with experiment.

Research paper thumbnail of Theoretical evaluation of the Be-2s2p² 4P hyperfine parameters and Be 2s2p ³Po electron-affinity

info:eu-repo/semantics/nonPublishe

Research paper thumbnail of Isotope shift in the electron affinity of beryllium

Journal of Physics B: Atomic, Molecular and Optical Physics, 2004

Research paper thumbnail of Ab initiocalculations of14N and15N hyperfine structures

Journal of Physics B: Atomic, Molecular and Optical Physics, 2010

Hyperfine structure parameters are calculated for the 2p 2 (3 P)3s 4 P J , 2p 2 (3 P)3p 4 P o J a... more Hyperfine structure parameters are calculated for the 2p 2 (3 P)3s 4 P J , 2p 2 (3 P)3p 4 P o J and 2p 2 (3 P)3p 4 D o J levels, using the ab initio multiconfiguration Hartree-Fock method. The theoretical hyperfine coupling constants are in complete disagreement with the experimental values of Jennerich et al. [1] deduced from the analysis of the near-infrared Doppler-free saturated absorption spectra.

Research paper thumbnail of Irreducible tensor form of the relativistic corrections to the M1 transition operator

Journal of Physics B: Atomic, Molecular and Optical Physics, 2009

The relativistic corrections to the magnetic dipole moment operator in the Pauli approximation we... more The relativistic corrections to the magnetic dipole moment operator in the Pauli approximation were derived originally by Drake [1]. In the present paper, we derive their irreducible tensor-operator form to be used in atomic structure codes adopting the Fano-Racah-Wigner algebra for calculating its matrix elements.

Research paper thumbnail of Theoretical evaluation of the 7,9 Be   2s2p 2 4 P 1/2,3/2,5/2 hyperfine structure parameters and Be 2s2p 3 P o electron affinity

Journal of Physics B: Atomic, Molecular and Optical Physics, 2003

Short title: Theoretical evaluation of the 7,9 Be − 2s2p 2 4 P 1/2,3/2,5/2 hyperfine structure pa... more Short title: Theoretical evaluation of the 7,9 Be − 2s2p 2 4 P 1/2,3/2,5/2 hyperfine structure parameters and Be 2s2p 3 P o electron-affinity

Research paper thumbnail of Saturation spectra of low lying states of Nitrogen: reconciling experiment with theory

The European Physical Journal D, 2010

The hyperfine constants of the levels 2p 2 (3 P)3s 4 PJ , 2p 2 (3 P)3p 4 P o J and 2p 2 (3 P)3p 4... more The hyperfine constants of the levels 2p 2 (3 P)3s 4 PJ , 2p 2 (3 P)3p 4 P o J and 2p 2 (3 P)3p 4 D o J , deduced by Jennerich et al. [Eur. Phys. J. D 40, 81 (2006)] from the observed hyperfine structures of the transitions 2p 2 (3 P)3s 4 PJ → 2p 2 (3 P)3p 4 P o J and 2p 2 (3 P)3s 4 PJ → 2p 2 (3 P)3p 4 D o J recorded by saturation spectroscopy in the near-infrared, strongly disagree with the ab initio values of Jönsson et al. [J. Phys. B: At. Mol. Opt. Phys. 43,115006 (2010)]. We propose a new interpretation of the recorded weak spectral lines. If the latter are indeed reinterpreted as crossover signals, a new set of experimental hyperfine constants is deduced, in very good agreement with the ab initio predictions.

Research paper thumbnail of Theoretical study of the hyperfine structure and isotope shifts in near-infrared transitions of atomic nitrogen

Sixth International Conference on Atomic and Molecular Data and Their Applications, Beijing (China)

Research paper thumbnail of Ab initio study of the hyperfine structure and isotope shifts of near-infrared transitions in neutral nitrogen

426th Wilhelm and Else Heraeus Seminar - Atomic Theory for Fundamental Interactions and Simple Sy... more 426th Wilhelm and Else Heraeus Seminar - Atomic Theory for Fundamental Interactions and Simple Systems in Strong Fields, Bad Honnef (Germany), January 18 - 21, 2009.

Research paper thumbnail of Hyperfine structure of near-infrared transitions in neutral nitrogen revisited

info:eu-repo/semantics/nonPublishe

Research paper thumbnail of Hyperfine structure of low-lying states of 14; 15N (Salamanca)

... 2 Laboratoire d'Electronique Quantique, Université des Sciences et de la Technologie... more ... 2 Laboratoire d'Electronique Quantique, Université des Sciences et de la Technologie Houari Boumediene, BP32, El-Alia, Algiers, ALGERIA 3 ... In 1943, Holmes [2] measured a surprisingly large variation of the specific mass isotope shifts from one multiplet component to another ...

Research paper thumbnail of Relativistic effects on the hyperfine structures of2p4(3P)3p2Do,4Do, and4Poin19F i

Physical Review A, 2013

The hyperfine interaction constants of the 2p 4 (3 P)3p 2 D o 3/2,5/2 , 4 D o 1/2−7/2 and 4 P o 1... more The hyperfine interaction constants of the 2p 4 (3 P)3p 2 D o 3/2,5/2 , 4 D o 1/2−7/2 and 4 P o 1/2−5/2 levels in neutral fluorine are investigated theoretically. Large-scale calculations are carried out using the multiconfiguration Hartree-Fock (MCHF) and Dirac-Hartree-Fock (MCDHF) methods. In the framework of the MCHF approach, the relativistic effects are taken into account in the Breit-Pauli approximation using non relativistic orbitals. In the fully relativistic approach, the orbitals are optimized using the Dirac-Coulomb Hamiltonian with correlation models inspired by the non relativistic calculations. Higher-order excitations are captured through multireference configuration interaction calculations including the Breit interaction. In a third (intermediate) approach, the Dirac-Coulomb-Breit Hamiltonian matrix is diagonalized in a relativistic configuration space built with non relativistic MCHF radial functions converted into Dirac spinors using the Pauli approximation. The magnetic dipole hyperfine structure constants calculated with the three relativistic models are consistent and reveal unexpectedly large effects of relativity for 2 D o 5/2 , 4 P o 3/2 and 4 P o 5/2. The agreement with the few available experimental values is satisfactory. The strong J-dependence of relativistic corrections on the hyperfine constants is investigated through the detailed analysis of the orbital, spin-dipole and contact relative contributions calculated with the non relativistic magnetic dipole operator.

Research paper thumbnail of Weak correlation and strong relativistic effects on the hyperfine interaction in fluorine

Physical Review A

In previous work devoted to ab initio calculations of hyperfine structure constants in nitrogen a... more In previous work devoted to ab initio calculations of hyperfine structure constants in nitrogen and fluorine atoms, we observed sizeable relativistic effects, a priori unexpected for such light systems, that can even largely dominate over electron correlation. We observed that the atomic wave functions calculated in the Breit-Pauli approximation describe adequately the relevant atomic levels and hyperfine structures, even in cases for which a small relativistic LS-term mixing becomes crucial. In the present work we identify new levels belonging to the spectroscopic terms 2p 4 (3 P)3d 2,4 (P, D, F) of the fluorine atom, for which correlation effects on the hyperfine structures are small, but relativistic LS-term admixtures are decisive to correctly reproduce the experimental values. The Breit-Pauli analysis of the hyperfine matrix elements nails cases with large cancellation, either between LS pairs for individual hyperfine operators, or between the orbital and the spin-dipole contributions. Multiconfiguration Dirac-Hartree-Fock calculations are performed to support the Breit-Pauli analysis.

Research paper thumbnail of Theoretical hyperfine structures of F19 i and O17 i

Physical Review A, 2018

Multiconfiguration Hartree-Fock (MCHF) and multiconfiguration Dirac-Hartree-Fock (MCDHF) calculat... more Multiconfiguration Hartree-Fock (MCHF) and multiconfiguration Dirac-Hartree-Fock (MCDHF) calculations are performed for the 2p 5 2 P o , 2p 4 (3 P)3s 4 P , 2p 4 (3 P)3s 2 P and 2p 4 (3 P)3p 4 S o states of 19 F I to determine their hyperfine constants. Several computing strategies are considered to investigate electron correlation and relativistic effects. High-order correlation contributions are included in MCHF calculations based on single and double multireference (SD-MR) expansions. The largest components of the single reference MCHF wave functions are selected to define the MR sets. In this scheme, relativistic corrections are evaluated in the Breit-Pauli approximation. A similar strategy is used for the calculation of MCDHF relativistic wave functions and hyperfine parameters. While correlation and relativistic corrections are found to be rather small for the ground state, we highlight large relativistic effects on the hyperfine constant A 3/2 of 2p 4 (3 P)3p 4 S o and, to a lesser extent, on A 1/2 of 2p 4 (3 P)3s 4 P. As expected for such a light system, electron correlation effects dominate over relativity in the calculation of the hyperfine interaction of all other levels considered. We also revisit the hyperfine constants of 2p 3 (4 S)3s 5 S o and 2p 3 (4 S)3p 5 P in 17 O using similar strategies. The results are found to be in excellent agreement with experiment.

Research paper thumbnail of Theoretical evaluation of the Be-2s2p² 4P hyperfine parameters and Be 2s2p ³Po electron-affinity

info:eu-repo/semantics/nonPublishe

Research paper thumbnail of Isotope shift in the electron affinity of beryllium

Journal of Physics B: Atomic, Molecular and Optical Physics, 2004

Research paper thumbnail of Ab initiocalculations of14N and15N hyperfine structures

Journal of Physics B: Atomic, Molecular and Optical Physics, 2010

Hyperfine structure parameters are calculated for the 2p 2 (3 P)3s 4 P J , 2p 2 (3 P)3p 4 P o J a... more Hyperfine structure parameters are calculated for the 2p 2 (3 P)3s 4 P J , 2p 2 (3 P)3p 4 P o J and 2p 2 (3 P)3p 4 D o J levels, using the ab initio multiconfiguration Hartree-Fock method. The theoretical hyperfine coupling constants are in complete disagreement with the experimental values of Jennerich et al. [1] deduced from the analysis of the near-infrared Doppler-free saturated absorption spectra.

Research paper thumbnail of Irreducible tensor form of the relativistic corrections to the M1 transition operator

Journal of Physics B: Atomic, Molecular and Optical Physics, 2009

The relativistic corrections to the magnetic dipole moment operator in the Pauli approximation we... more The relativistic corrections to the magnetic dipole moment operator in the Pauli approximation were derived originally by Drake [1]. In the present paper, we derive their irreducible tensor-operator form to be used in atomic structure codes adopting the Fano-Racah-Wigner algebra for calculating its matrix elements.

Research paper thumbnail of Theoretical evaluation of the 7,9 Be   2s2p 2 4 P 1/2,3/2,5/2 hyperfine structure parameters and Be 2s2p 3 P o electron affinity

Journal of Physics B: Atomic, Molecular and Optical Physics, 2003

Short title: Theoretical evaluation of the 7,9 Be − 2s2p 2 4 P 1/2,3/2,5/2 hyperfine structure pa... more Short title: Theoretical evaluation of the 7,9 Be − 2s2p 2 4 P 1/2,3/2,5/2 hyperfine structure parameters and Be 2s2p 3 P o electron-affinity

Research paper thumbnail of Saturation spectra of low lying states of Nitrogen: reconciling experiment with theory

The European Physical Journal D, 2010

The hyperfine constants of the levels 2p 2 (3 P)3s 4 PJ , 2p 2 (3 P)3p 4 P o J and 2p 2 (3 P)3p 4... more The hyperfine constants of the levels 2p 2 (3 P)3s 4 PJ , 2p 2 (3 P)3p 4 P o J and 2p 2 (3 P)3p 4 D o J , deduced by Jennerich et al. [Eur. Phys. J. D 40, 81 (2006)] from the observed hyperfine structures of the transitions 2p 2 (3 P)3s 4 PJ → 2p 2 (3 P)3p 4 P o J and 2p 2 (3 P)3s 4 PJ → 2p 2 (3 P)3p 4 D o J recorded by saturation spectroscopy in the near-infrared, strongly disagree with the ab initio values of Jönsson et al. [J. Phys. B: At. Mol. Opt. Phys. 43,115006 (2010)]. We propose a new interpretation of the recorded weak spectral lines. If the latter are indeed reinterpreted as crossover signals, a new set of experimental hyperfine constants is deduced, in very good agreement with the ab initio predictions.

Research paper thumbnail of Theoretical study of the hyperfine structure and isotope shifts in near-infrared transitions of atomic nitrogen

Sixth International Conference on Atomic and Molecular Data and Their Applications, Beijing (China)

Research paper thumbnail of Ab initio study of the hyperfine structure and isotope shifts of near-infrared transitions in neutral nitrogen

426th Wilhelm and Else Heraeus Seminar - Atomic Theory for Fundamental Interactions and Simple Sy... more 426th Wilhelm and Else Heraeus Seminar - Atomic Theory for Fundamental Interactions and Simple Systems in Strong Fields, Bad Honnef (Germany), January 18 - 21, 2009.

Research paper thumbnail of Hyperfine structure of near-infrared transitions in neutral nitrogen revisited

info:eu-repo/semantics/nonPublishe

Research paper thumbnail of Hyperfine structure of low-lying states of 14; 15N (Salamanca)

... 2 Laboratoire d'Electronique Quantique, Université des Sciences et de la Technologie... more ... 2 Laboratoire d'Electronique Quantique, Université des Sciences et de la Technologie Houari Boumediene, BP32, El-Alia, Algiers, ALGERIA 3 ... In 1943, Holmes [2] measured a surprisingly large variation of the specific mass isotope shifts from one multiplet component to another ...

Research paper thumbnail of Relativistic effects on the hyperfine structures of2p4(3P)3p2Do,4Do, and4Poin19F i

Physical Review A, 2013

The hyperfine interaction constants of the 2p 4 (3 P)3p 2 D o 3/2,5/2 , 4 D o 1/2−7/2 and 4 P o 1... more The hyperfine interaction constants of the 2p 4 (3 P)3p 2 D o 3/2,5/2 , 4 D o 1/2−7/2 and 4 P o 1/2−5/2 levels in neutral fluorine are investigated theoretically. Large-scale calculations are carried out using the multiconfiguration Hartree-Fock (MCHF) and Dirac-Hartree-Fock (MCDHF) methods. In the framework of the MCHF approach, the relativistic effects are taken into account in the Breit-Pauli approximation using non relativistic orbitals. In the fully relativistic approach, the orbitals are optimized using the Dirac-Coulomb Hamiltonian with correlation models inspired by the non relativistic calculations. Higher-order excitations are captured through multireference configuration interaction calculations including the Breit interaction. In a third (intermediate) approach, the Dirac-Coulomb-Breit Hamiltonian matrix is diagonalized in a relativistic configuration space built with non relativistic MCHF radial functions converted into Dirac spinors using the Pauli approximation. The magnetic dipole hyperfine structure constants calculated with the three relativistic models are consistent and reveal unexpectedly large effects of relativity for 2 D o 5/2 , 4 P o 3/2 and 4 P o 5/2. The agreement with the few available experimental values is satisfactory. The strong J-dependence of relativistic corrections on the hyperfine constants is investigated through the detailed analysis of the orbital, spin-dipole and contact relative contributions calculated with the non relativistic magnetic dipole operator.