The hyperfine energy levels of alkali metal dimers: ground-state polar molecules in electric and magnetic fields

TL;DR

This paper calculates hyperfine energy levels of heteronuclear alkali metal dimers, crucial for ultracold molecule production, using density-functional theory to explore their structure under electric and magnetic fields.

Contribution

It provides detailed hyperfine structure calculations for RbK and RbCs molecules, including nuclear quadrupole and magnetic coupling constants, under external fields.

Findings

Zero-field splittings are dominated by electron-mediated nuclear spin-spin coupling.

Splittings are a few kHz for RbK and tens of kHz for RbCs.

Hyperfine structure insights aid in ultracold molecule experiments.

Abstract

We investigate the energy levels of heteronuclear alkali metal dimers in levels correlating with the lowest rotational level of the ground electronic state, which are important in efforts to produce ground-state ultracold molecules. We use density-functional theory to calculate nuclear quadrupole and magnetic coupling constants for RbK and RbCs and explore the hyperfine structure in the presence of electric and magnetic fields. For nonrotating states, the zero-field splittings are dominated by the electron-mediated part of the nuclear spin-spin coupling. They are a few kHz for RbK isotopologs and a few tens of kHz for RbCs isotopologs.