Ab initioestimations of the isotope shift for the first three elements of the K isoelectronic sequence

Abstract

Isotope shifts (ISs) of ${D}_{1}\phantom{\rule{4.pt}{0ex}}(ns\phantom{\rule{0.16em}{0ex}}^{2}S_{1/2}\ensuremath{\rightarrow}np\phantom{\rule{0.16em}{0ex}}^{2}P_{1/2})$ and ${D}_{2}\phantom{\rule{4.pt}{0ex}}(ns\phantom{\rule{0.16em}{0ex}}^{2}S_{1/2}\ensuremath{\rightarrow}np\phantom{\rule{0.16em}{0ex}}^{2}P_{3/2})$ transitions for the first three elements of the K isoelectronic sequence are calculated with all-order correlated relativistic coupled-cluster theory. To get precise ab initio results, all the orbitals of the reference states have been optimized by a linear regression technique. Some of the important IS estimations reported here were not available in literature. Interesting features of odd-even staggering and magic neutron number effects are also observed in the case of volume shift calculations. Energy-level corrections for a few levels due to a change in the nuclear model from a point nucleus to a Fermi nucleus have been studied with interesting correlation features and compared with other theoretical results available in literature.