Spin controlled atom-ion inelastic collisions

The control of ultracold collisions between neutral atoms is an extensive and successful field of study. The tools developed in this field allow for ultracold chemical reactions to be managed using magnetic fields1, light fields2 and spin-state manipulation of the colliding particles3 among other methods. Control of chemical reactions in ultracold atom-ion collisions is a young and growing field of research. Recently, the collision energy4 and the ion electronic state5–8 were used to control atom-ion interactions. Here, we demonstrate spincontrolled atom-ion inelastic processes. In our experiment, both spin-exchange and chargeexchange 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. Charge-exchange collisions induced by electron transfer are 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. ∗Current address: Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland