Charge Exchange Dynamics in Cold Collisions of $^{40}$CaH$^+$ and $^{39}$K

TL;DR

This study observes charge-exchange collisions between $^{40}$CaH$^+$ ions and ultracold $^{39}$K atoms, finding suppressed rates and highlighting complex quantum dynamics in molecular ion-atom interactions.

Contribution

It provides experimental measurements of charge-exchange rates in a molecular ion-atom system and combines quantum-chemical modeling to explore underlying mechanisms.

Findings

Charge-exchange rate is significantly suppressed compared to Langevin rate.

Quantum-chemical calculations do not fully explain the observed rate.

Demonstrates the potential of cold hybrid ion-atom systems for complex chemical studies.

Abstract

We report the observation of charge-exchange collisions between trapped calcium monohydride molecular ions ($^{40}$CaH$^+$) and ultracold potassium atoms ($^{39}$K) in a hybrid ion-atom trap. The measured charge-exchange rate coefficient is significantly suppressed relative to the Langevin rate constant for the system. We use quantum-chemical calculations to model the (CaH-K)$^+$ system in the ground and excited electronic states and to identify possible charge-exchange mechanisms. Our calculations do not fully explain the measured rate, highlighting the need for a full-dimensional quantum treatment that includes vibrational motion and intermediate complex formation. Our work demonstrates that cold hybrid ion-atom platforms with molecular ions enable access to richer chemical complexity and collisional dynamics inaccessible in purely atomic systems.