Ab initio calculation of the isotope shift in the fine structure of C II and N II.

Abstract

The nuclear-motion fine-structure isotope shifts in the ground states of C ii and N ii are computed by use of many-body perturbation theory. There are three different kinds of nuclear motion corrections to the atomic fine structure: normal mass effects on the spin-orbit and spin-spin interactions, electron-nucleus relativistic interactions, and higher-order cross terms between the specific-mass-shift operator and spin-dependent interactions. All three types of corrections have been considered and computed to third order in the many-body perturbation expansion. The computed results are in excellent agreement with recent accurate experimental values.