Weak Correlation and Strong Relativistic Effects on the Hyperfine Interaction in Fluorine
Abstract
In previous work devoted to {\it 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 BreitPauli 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 BreitPauli 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 spindipole contributions. Multiconfiguration DiracHartreeFock calculations are performed to support the BreitPauli analysis.
 Publication:

arXiv eprints
 Pub Date:
 August 2021
 arXiv:
 arXiv:2108.01116
 Bibcode:
 2021arXiv210801116Z
 Keywords:

 Physics  Atomic Physics