Photoassociation of a cold atom-molecule pair: long-range quadrupole-quadrupole interactions

TL;DR

This paper develops a formalism to calculate long-range quadrupole-quadrupole interactions between excited atoms and molecules, demonstrating the potential for photoassociation of cold atom-molecule pairs and extending to cold tetramers.

Contribution

It introduces a multipolar expansion formalism for electrostatic interactions between excited atoms and molecules with quadrupole moments, enabling analysis of cold molecule formation.

Findings

Quadrupole-quadrupole interactions can bind atom-molecule pairs at large separations.

Numerical results for Cs(6P) and Cs2 show attractive long-range potentials.

The formalism suggests promising prospects for photoassociation of cold atom-dimer pairs.

Abstract

The general formalism of the multipolar expansion of electrostatic interactions is applied to the calculation the potential energy between an excited atom (without fine structure) and a ground state diatomic molecule at large separations. Both partners exhibit a permanent quadrupole moment, so that their mutual quadrupole-quadrupole long-range interaction is attractive enough to bind trimers. Numerical results are given for an excited Cs(6P) atom and a ground state Cs2 molecule. The prospects for achieving photoassociation of a cold atom/dimer pair is thus discussed and found promising. The formalism can be easily generalized to the long-range interaction between molecules to investigate the formation of cold tetramers.