Controlled state-to-state atom-exchange reaction in an ultracold atom-dimer mixture

TL;DR

This paper reports the direct observation and control of a quantum state-to-state atom-exchange reaction in an ultracold atom-dimer mixture, revealing detailed reaction dynamics and enabling potential quantum simulation applications.

Contribution

It demonstrates the first controlled, state-resolved ultracold atom-exchange reaction with measurable reaction rates and quantum state characterization.

Findings

Reaction rate up to 1.1×10⁻⁹ cm³/s measured

Reaction can be switched on or off via magnetic field

Reaction involves spin-exchange interaction, useful for quantum simulations

Abstract

Ultracold molecules offer remarkable opportunities to study chemical reactions at nearly zero temperature. Although significant progresses have been achieved in exploring ultracold bimolecular reactions, the investigations are usually limited to measurements of the overall loss rates of the reactants. Detection of the reaction products will shed new light on understanding the reaction mechanism and provide a unique opportunity to study the state-to-state reaction dynamics. Here we report on the direct observation of an exoergic atom-exchange reaction in an ultracold atom-dimer mixture. Both the atom and molecule products are observed and the quantum states are characterized. By changing the magnetic field, the reaction can be switched on or off, and the reaction rate can be controlled. The reaction is efficient and we have measured a state-to-state reaction rate of up to $1.1(3)\times10^{-9}$cm$^{3}/$s from the time evolution of the reactants and products. Our work represents the realization of a controlled quantum state selected/resolved ultracold reaction. The atom-exchange reaction observed is also an effective spin-exchange interaction between the Feshbach molecules and the fermionic atoms and may be exploited to implement quantum simulations of the Kondo effect with ultracold atoms and molecules.