Ultracold atom-dimer long-range interactions beyond the $1/R^{n}$ expansion

TL;DR

This paper develops a detailed theoretical model of long-range interactions between ultracold alkali-metal dimers and atoms, revealing complex behaviors beyond traditional $1/R^{n}$ expansions, with implications for ultracold molecule formation.

Contribution

It introduces a comprehensive description of long-range interactions including quadrupole-quadrupole and dipole-dipole effects, accounting for rotational couplings and avoided crossings.

Findings

Adiabatic potential energy curves show avoided crossings.

The $1/R^{n}$ expansion fails near certain energy scales.

Results suggest pathways for ultracold trimer photoassociation.

Abstract

We investigate theoretically the combination of first-order quadrupole-quadrupole and second-order dipole-dipole effects on the long-range electrostatic interactions between a ground-state homonuclear alkali-metal dimer and an excited alkali-metal atom. As the electrostatic energy is comparable to the dimer rotational structure, we develop a general description of the long-range interactions which allows for couplings between the dimer rotational levels. The resulting adiabatic potential energy curves, which exhibit avoided crossings, cannot be expanded on the usual $1/R^{n}$ series. We study in details the breakdown of this approximation in the particular case Cs$_{2}+$Cs. Our results are found promising in the prospect of accomplishing the photoassociation of ultracold trimers.