A Simple Quantum Model of Ultracold Polar Molecule Collisions

TL;DR

This paper introduces a simplified quantum model to predict ultracold polar molecule collision rates, accounting for long-range forces and electric field effects, applicable to reactive and non-reactive species.

Contribution

It provides a unified formalism that reduces complex scattering processes to essential features, enabling easy parametrization of electric-field dependence in ultracold molecule collisions.

Findings

Model accurately predicts collision rates for KRb and RbCs.

Electric-field dependence can be parametrized with two fitting parameters.

Formalism simplifies the analysis of ultracold molecular collisions.

Abstract

We present a unified formalism for describing chemical reaction rates of trapped, ultracold molecules. This formalism reduces the scattering to its essential features, namely, a propagation of the reactant molecules through a gauntlet of long-range forces before they ultimately encounter one another, followed by a probability for the reaction to occur once they do. In this way, the electric-field dependence should be readily parametrized in terms of a pair of fitting parameters (along with a $C_6$ coefficient) for each asymptotic value of partial wave quantum numbers $|L,M \rangle$. From this, the electric field dependence of the collision rates follows automatically. We present examples for reactive species such as KRb, and non-reactive species, such as RbCs.