Quantum Reactive Scattering of Ultracold Atoms and Molecules: Universality and Chaotic Dynamics

TL;DR

This paper investigates ultracold chemical reactions involving KRb and K atoms, revealing chaotic dynamics and universality in reaction rates at near-zero temperatures through ab initio calculations and quantum-mechanical analysis.

Contribution

It provides the first accurate ab initio potential energy surface for KRbK and demonstrates chaotic behavior in ultracold reactions, contrasting with lighter systems.

Findings

Reaction rates follow a Poissonian distribution.

Chaotic dynamics are linked to the complex's short-range potential.

Comparison shows lighter systems exhibit non-chaotic, random behavior.

Abstract

A fundamental question in the study of chemical reactions is how reactions proceed at a collision energy close to absolute zero. This question is no longer hypothetical: quantum degenerate gases of atoms and molecules can now be created at temperatures lower than a few tens of nanoKelvin. In this work we consider the benchmark ultracold reaction between, the most-celebrated ultracold molecule, KRb and K. For the first time we map out an accurate ab initio ground state potential energy surface of the KRbK complex in full dimensionality and report numerically exact quantum-mechanical reaction dynamics. The distribution of rotationally resolved rates is shown to be Poissonian. An analysis of the hyperspherical adiabatic potential curves explains this statistical character revealing a chaotic distribution for the short-range collision complex that plays a key role in governing the reaction outcome. We compare this with a lighter system with a smaller density of states (here the LiYbLi trimer) which displays random, and not chaotic, behavior.