Spin hierarchy in van der Waals molecule formation via ultracold three-body recombination

TL;DR

This paper theoretically explores the spin state distribution of weakly bound diatomic van der Waals molecules formed through ultracold three-body recombination, revealing a hierarchy of spin propensity rules at zero magnetic field.

Contribution

It uncovers a two-level hierarchy of spin propensity rules governing product states, highlighting the conservation of hyperfine and spin components and their dependence on atomic interactions.

Findings

Nearly all molecular products conserve the total hyperfine spin.

A secondary propensity favors conservation of certain spin components.

Spin sensitivity could enable control of reaction rates in ultracold chemistry.

Abstract

We theoretically investigate the product-state distribution of weakly bound diatomic van der Waals molecules via ultracold three-body recombination of bosonic alkali atoms. We find a two-level hierarchy of spin propensity rules at zero magnetic field. The primary propensity rule states that nearly all molecular products conserve the total hyperfine spin of reactant atomic pairs, while molecular products not conserving the total spin are highly suppressed. For the dominant molecular products, there is a secondary propensity to conserve certain spin components of the reactant pair such as the atomic hyperfine spins, or the total electronic or nuclear spins. The second propensity varies across species and depends fundamentally on the interplay between effective electronic exchange and hyperfine interactions. The spin sensitivity of product-state distribution can potentially open up new avenues for controlling state-to-state reaction rates in ultracold three-body recombination.