Long-range interactions between polar alkali-metal diatoms in external electric fields

TL;DR

This study calculates long-range interactions between identical polar alkali-metal diatoms in external electric fields, revealing regimes of molecular orientation and proposing a mechanism for forming ultracold tetramers.

Contribution

It provides accurate quantum chemistry calculations of interactions for ten species and explores electric field effects on molecular orientation and association mechanisms.

Findings

Huge van der Waals interactions in free space for eight species

Electric fields can control molecular orientation without a preferred laboratory frame direction

Proposed mechanism for ultracold tetramer formation via radiative association

Abstract

We computed the long-range interactions between two identical polar bialkali molecules in their rovibronic ground level, for all ten species involving Li, Na, K, Rb and Cs, using accurate quantum chemistry results combined with available spectroscopic data. Huge van der Waals interaction is found for eight species in free space. The competition of the van der Waals interaction with the dipole-dipole interaction induced by an external electric field parallel or perpendicular to the intermolecular axis is investigated by varying the electric field magnitude and the intermolecular distance. Our calculations predict a regime with the mutual orientation of the two molecules but with no preferential direction in the laboratory frame. A mechanism for the stimulated one-photon radiative association of a pair of ultracold polar molecules into ultracold tetramers is proposed, which would open the way towards the optical manipulation of ultracold polyatomic molecules.