Ab initio Calculations of Electric Dipole Polarizabilities in the Li, Na and K Atoms

TL;DR

This paper presents ab initio calculations of electric dipole polarizabilities in Li, Na, and K atoms using various theoretical methods, highlighting the importance of pair-correlation effects and comparing results with experiments.

Contribution

It provides a comprehensive comparison of multiple computational approaches for polarizability calculations in alkali atoms, emphasizing the role of correlation effects.

Findings

DHF and RPA results are similar.

MBPT(3) and RCCSD results are similar.

Core-valence contributions are negligible.

Abstract

We carry out first-principle calculations of scalar and tensor components of the static electric dipole polarizabilities of six low-lying states of lithium (Li), sodium (Na) and potassium (K) alkali atoms in the linear response approach. Results are compared from the Dirac-Hartree-Fock (DHF) method, third-order many-body perturbation theory (MBPT(3) method), random phase approximation (RPA) and singles and doubles approximated relativistic coupled-cluster theory (RCCSD method). We find the DHF and RPA results are close to each other, while the MBPT(3) and RCCSD results are close to each other. This suggests that pair-correlation effects play significant roles over core-polarization effects to determine these quantities accurately in the above alkali atoms. We also compare contributions arising through the core, core-valence and valence correlations through all the methods in Li, Na and K, which show that the core-valence contributions are negligibly small in all the methods and there is no particular trends of the core and valence correlation contributions with the size of the atom. Uncertainties to the RCCSD results are estimated to quote the final values, and they are compared with the previous calculations and experimental results.