Universal rate constants for reactive collisions of ultracold molecules

TL;DR

This paper introduces a quantum defect model that provides universal expressions for collision rates of ultracold molecules, explaining experimental results and predicting rate constants independent of short-range dynamics.

Contribution

The paper presents an analytic quantum defect model that predicts universal collision rate constants for ultracold molecules, applicable when reaction probabilities are high.

Findings

Model accurately predicts measured rate constants for ultracold 40K87Rb molecules.

Provides analytic expressions for s- and p-wave collision rates.

Explains the universality of certain ultracold molecular collision rates.

Abstract

A simple quantum defect model gives analytic expressions for the complex scattering length and threshold collision rates of ultracold molecules. If the probability of reaction in the short-range part of the collision is high, the model gives universal rate constants for s- and p-wave collisions that are independent of short-range dynamics. This model explains the magnitudes of the recently measured rate constants for collisions of two ultracold 40K87Rb molecules, or an ultracold 40K atom with the 40K87Rb molecule [Ospelkaus et al., Science 327, 853 (2010)].