Long-range interactions between the alkali-metal atoms and alkaline earth ions

TL;DR

This paper provides detailed theoretical calculations of long-range interaction potentials between alkali-metal atoms and alkaline earth ions, crucial for cold atom physics applications, by deriving dispersion and induction coefficients from advanced quantum methods.

Contribution

It systematically computes interaction coefficients and polarizabilities for Li, Na, K, Rb atoms with Ca+, Ba+, Sr+, Ra+ ions using relativistic coupled-cluster and RPA methods, verifying accuracy against existing data.

Findings

Accurate dispersion and induction coefficients for atom-ion pairs.

Calculated polarizabilities consistent with other theoretical and experimental results.

Graphical potentials illustrating interactions across different atom-ion combinations.

Abstract

Accurate knowledge of interaction potentials among the alkali atoms and alkaline earth ions is very useful in the studies of cold atom physics. Here we carry out theoretical studies of the long-range interactions among the Li, Na, K, and Rb alkali atoms with the Ca$^+$, Ba$^+$, Sr$^+$, and Ra$^+$ alkaline earth ions systematically which are largely motivated by their importance in a number of applications. These interactions are expressed as a power series in the inverse of the internuclear separation $R$. Both the dispersion and induction components of these interactions are determined accurately from the algebraic coefficients corresponding to each power combination in the series. Ultimately, these coefficients are expressed in terms of the electric multipole polarizabilities of the above mentioned systems which are calculated using the matrix elements obtained from a relativistic coupled-cluster method and core contributions to these quantities from the random phase approximation. We also compare our estimated polarizabilities with the other available theoretical and experimental results to verify accuracies in our calculations. In addition, we also evaluate the lifetimes of the first two low-lying states of the ions using the above matrix elements. Graphical representation of the interaction potentials versus $R$ are given among all the considered atoms and ions.