Non-adiabatic quantum interference effects and chaoticity in the ultracold Li + LiNa $\to$ Li$_2$ + Na reaction

TL;DR

This study reveals how non-adiabatic quantum interference effects, caused by conical intersections, significantly influence ultracold Li + LiNa reactions, with potential applications in quantum control and indications of chaotic dynamics.

Contribution

First principles quantum dynamics calculations uncover non-adiabatic interference effects and chaotic behavior in ultracold alkali metal reactions, a largely unexplored area.

Findings

Quantum interference alters ultracold reaction rates.

Poisson distribution of product states indicates chaos.

Interference effects could enable quantum control.

Abstract

Electronically non-adiabatic effects play an important role in many chemical reactions. How these effects manifest in cold and ultracold chemistry remain largely unexplored. Here, through first principles non-adiabatic quantum dynamics calculations of the Li + LiNa $\to$ Li$_2$ + Na chemical reaction, it is shown that non-adiabatic dynamics induces quantum interference effects that dramatically alter the ultracold rotationally resolved reaction rate coefficients. The interference effect arises from a conical intersection between the ground and an excited electronic state that is energetically accessible even for ultracold collisions. These unique interference effects might be exploited for quantum control applications as a quantum molecular switch. A statistical analysis of rotational populations of the Li$_2$ product reveals a Poisson distribution implying an underlying classically chaotic dynamics. The Poisson distribution is robust and amenable to experimental verification and appears to be a universal property of ultracold reactions involving alkali metal dimers.