State-selected ion-molecule reactions with Coulomb-crystallized molecular ions in traps

TL;DR

This study demonstrates the use of Coulomb-crystallized molecular ions in ion-molecule reactions, enabling state- and energy-controlled experiments with high sensitivity, and provides detailed insights into charge transfer processes through simulations.

Contribution

First application of Coulomb-crystallized molecular ions in reaction studies, allowing precise control and analysis of state-specific ion-molecule reactions.

Findings

Successful preparation of state-selected ions in traps.

Observation of energy transfer during charge transfer.

Agreement between experimental results and trajectory simulations.

Abstract

State-selected Coulomb-crystallized molecular ions were employed for the first time in ion-molecule reaction studies using the prototypical charge-transfer process $\mathrm{N_2^++N_2\rightarrow N_2+N_2^+}$ as an example. By preparing the reactant ions in a well-defined rovibrational state and localizing them in space by sympathetic cooling to millikelvin temperatures in an ion trap, state- and energy-controlled reaction experiments with sensitivities on the level of single ions were performed. The experimental results were interpreted with quasi-classical trajectory simulations on a six-dimensional potential-energy surface which provided detailed insight into translation-to-rotation energy transfer occurring during charge transfer between N$_2$ and N$_2^+$.