Probing isotope effects in chemical reactions using single ions

TL;DR

This study uses single-ion reaction events to investigate isotope effects in reactions between Mg+ ions and molecular hydrogen, demonstrating a method that can yield quantitative insights even with limited reaction data.

Contribution

It introduces a novel approach using single-ion reactions to analyze isotope effects, suitable for rare or unstable isotopic species.

Findings

Branching ratio for MgD+ vs MgH+ exceeds 5.

Decay probabilities of intermediate complexes are similar across isotopes.

Few reaction events suffice for quantitative isotope effect analysis.

Abstract

Isotope effects in reactions between Mg+ in the 3p 2P3/2 excited state and molecular hydrogen at thermal energies are studied through single reaction events. From only ~250 reactions with HD, the branching ratio between formation of MgD+ and MgH+ is found to be larger than 5. From additional 65 reactions with H2 and D2 we find that the overall decay probability of the intermediate MgH2+, MgHD+ or MgD2+ complexes is the same. Our study shows that few single ion reactions can provide quantitative information on ion-neutral reactions. Hence, the method is well-suited for reaction studies involving rare species, e.g., rare isotopes or short-lived unstable elements.