Spin controlled atom-ion inelastic collisions

TL;DR

This paper demonstrates control over inelastic atom-ion collisions at ultracold temperatures by manipulating the atomic spin state, affecting reaction rates and enabling precise control of chemical processes.

Contribution

It introduces spin-state control of inelastic atom-ion collisions, showing how atomic spin preparation influences reaction rates in ultracold Rb-Sr$^+$ mixtures.

Findings

Spin-exchange collisions polarize the ion spin.

Charge-exchange rate varies with atomic spin state.

Experimental results agree with theoretical predictions.

Abstract

The control of the ultracold collisions between neutral atoms is an extensive and successful field of study. The tools developed allow for ultracold chemical reactions to be managed using magnetic fields, light fields and spin-state manipulation of the colliding particles among other methods. The control of chemical reactions in ultracold atom-ion collisions is a young and growing field of research. Recently, the collision energy and the ion electronic state were used to control atom-ion interactions. Here, we demonstrate spin-controlled atom-ion inelastic processes. In our experiment, both spin-exchange and charge-exchange reactions are controlled in an ultracold Rb-Sr$^+$ mixture by the atomic spin state. We prepare a cloud of atoms in a single hyperfine spin-state. Spin-exchange collisions between atoms and ion subsequently polarize the ion spin. Electron transfer is only allowed for (RbSr)$^+$ colliding in the singlet manifold. Initializing the atoms in various spin states affects the overlap of the collision wavefunction with the singlet molecular manifold and therefore also the reaction rate. We experimentally show that by preparing the atoms in different spin states one can vary the charge-exchange rate in agreement with theoretical predictions.