Configuration Interaction and Many‐Body Perturbation Theory: Application to Scandium, Titanium, and Iodine

Abstract

A number of atoms and ions with complex valence configurations are considered as candidates for atomic clocks with high sensitivity to the possible variation of the fine-structure constant. Present level of the theory is not sufficient to predict frequencies of the clock transitions with accuracy, required for the experiment. Here an approach is tested, where the second-order perturbation theory is used to iteratively saturate configuration space for valence electrons. On the examples of scandium, titanium, and iodine, it is demonstrated that this improves the efficiency of the CI+MBPT method for systems with strong configuration interaction and/or more than three valence electrons.

Many-Electron QED with Redefined Vacuum Approach

“…In recent years, the accuracy of large-scale correlation calculations of transition energies in many-electron atoms and ions drastically improved [2,44,[53][54][55][56]. Various highly efficient computer codes have been developed for this purpose [57][58][59][60][61][62].…”

Many-Electron QED with Redefined Vacuum Approach

“…In recent years, the accuracy of large-scale correlation calculations of transition energies in many-electron atoms and ions drastically improved [2,33,[42][43][44][45]. Various highly efficient computer codes have been developed for this purpose [46][47][48][49][50][51].…”

Combination of the Perturbation Theory with Configuration Interaction Method

“…Recently there were several attempts [25][26][27][28] to develop an effective and fast CI+VPT method to speed up calculations for such systems, where straightforward CI calculations are impossible. Application of these methods for systems with a large number of valence electrons was demonstrated in Refs.…”