Natural orbitals in multiconfiguration calculations of hyperfine-structure parameters

Abstract

We are reinvestigating the hyperfine structure of sodium using a fully relativistic multiconfiguration approach. In the fully relativistic approach, the computational strategy somewhat differs from the original nonrelativistic counterpart used by P. Jönsson et al., Phys. Rev. A 53, 4021 (1996). Numerical instabilities force us to use a layer-by-layer approach that has some broad unexpected effects. Core correlation is found to be significant and therefore should be described in an adequate orbital basis. The natural-orbital basis provides an interesting alternative to the orbital basis from the layer-by-layer approach, allowing us to overcome some deficits of the latter, giving rise to magnetic dipole hyperfine structure constant values, in excellent agreement with observations. Effort is made to assess the reliability of the natural-orbital bases and to illustrate their efficiency.

Ab initio electronic factors of the A and B hyperfine structure constants for the 5s25p6s<

“…Natural orbitals were recently used, as an efficient tool to overcome the limitation of the layer-by-layer optimization scheme, to estimate hyperfine structure constants in Na I. Thanks to the radial reorganization of the orbitals, the spectroscopic orbitals are ultimately contracted, which affects both M1 and E2 electronic hyperfine factors [72]. Further investigations on the usefulness of the natural orbitals in the calculations of hyperfine structures are in progress.…”

“…III A 4, the sensitivity of the SrD-SR-MCDHF+RCI and SrD-MR-MCDHF+RCI results to the orbital basis was investigated by combining the radial orbital basis obtained in one of these two computational approaches with the CSF expansions used in the RCI computations of the other approach. As seen in Table V, these combinations gave rise to B el The deviation of the calculated M1 hyperfine constant from the experimental value |A theor − A expt | is often assumed to be a measure of the overall accuracy of the hyperfine structure calculations [35,50,72] The extreme sensitivity of A el [ 1 P o 1 ] to correlation models is not really surprising if one performs calculations using the quasirelativistic Hartree-Fock and Breit-Pauli [47] method in the single-configuration approximation. In the Breit-Pauli (BP) scheme, the low value of the ratio A el [ 1 P o 1 ]/A el [ 3 P o 1 ] can indeed be understood.…”

Electronic isotope shift factors for the Ir 5d76s24F9/2Schiffmann1, Godefroid2 2021Journal of Quantitative Spectroscopy and Radiative TransferSelf Cite6100View full textAdd to dashboardCite

“…Considering the sixth J = 9 / 2 -odd parity level, the leading configurations are 5 d 7 6 s 6 p , 5 d 8 6 p and 5 d 6 6 s 2 6 p . We expect these three configurations to have significantly different electronic densities at the origin, according to their respective occupation number of the s orbitals [30] . Thanks to a simple occupation number-based analysis, we expect the following inequalities ρ(5 d 8 6 p) < ρ(5 d 7 6 s 6 p) < ρ(5 d 6 6 s 2 6 p) (14) to hold, in which the density increases with the occupation number of the 6 s orbital.…”

“…The second step of the calculations, i.e., the generation of the orbital basis set, is performed layer-by-layer [30] . An individual layer consists of at most one correlation orbital per l -symmetry.…”

Ab initio calculations of the hyperfine structure of 109Cd, 109Cd+ and reevaluation of the nuclear quadrupole moment Q(109Cd)

“…Q value from various works in barn (b). Cd atom the error bar for the determination of Q[14,15,27,33]. Considering the uncertainties of A for the 2 P 3/2 , and 3 P 1,2 states, an average error bar of 22 mb is obtained.…”