Photoassociation of a cold atom-molecule pair II: second order perturbation approach

TL;DR

This paper develops a second-order perturbation theory to analyze long-range electrostatic interactions between excited atoms and diatomic molecules, with implications for cold atom-molecule photoassociation.

Contribution

It introduces a second-order perturbation approach to model electrostatic interactions in atom-molecule pairs at large distances, extending understanding of photoassociation processes.

Findings

Quadrupole-quadrupole and van der Waals interactions compete with rotational energy.

Perturbative approach valid for distances > 100 a.u.

Photoassociation likely efficient regardless of molecular rotational energy.

Abstract

The electrostatic interaction between an excited atom and a diatomic ground state molecule in an arbitrary rovibrational level at large mutual separations is investigated with a general second-order perturbation theory, in the perspective of modeling the photoassociation between cold atoms and molecules. We find that the combination of quadrupole-quadrupole and van der Waals interactions compete with the rotational energy of the dimer, limiting the range of validity of the perturbative approach to distances larger than 100 a.u.. Numerical results are given for the long-range interaction between Cs and Cs$_2$, showing that the photoassociation is probably efficient whatever the Cs$_2$ rotational energy.