Symmetry breaking in sticky collisions between ultracold molecules

TL;DR

This paper develops a quantitative theory for symmetry-breaking interactions affecting sticky collisions of ultracold molecules, showing electric fields can induce angular momentum non-conservation while nuclear spin remains conserved, with slow loss mechanisms identified.

Contribution

It provides a detailed classical simulation-based analysis of the strength of symmetry-breaking interactions in ultracold molecular collisions, highlighting the effects of electric fields and radiation.

Findings

Electric fields as small as 10 V/cm can break angular momentum conservation.

Nuclear spin remains conserved during collisions.

Loss due to spontaneous emission and black-body radiation is slow.

Abstract

Ultracold molecules undergo "sticky collisions" that result in loss even for chemically nonreactive molecules. Sticking times can be enhanced by orders of magnitude by interactions that lead to non-conservation of nuclear spin or total angular momentum. We present a quantitative theory of the required strength of such symmetry-breaking interactions based on classical simulation of collision complexes. We find static electric fields as small as $10$~V/cm can lead to non-conservation of angular momentum, while we find nuclear spin is conserved during collisions. We also compute loss of collision complexes due to spontaneous emission and absorption of black-body radiation, which are found to be slow.