Probing isotope effects in chemical reactions using single ions

Area of Science:

• Chemical Kinetics
• Physical Chemistry
• Isotope Effects

Background:

• Magnesium ion (Mg+) reactions with molecular hydrogen are crucial for understanding ion-neutral interactions.
• Investigating isotope effects provides insights into reaction mechanisms and dynamics.

Purpose of the Study:

• To investigate isotope effects in the reaction of Mg+ (in the 3p{2}P{3/2} excited state) with molecular hydrogen (H2, D2, HD) at thermal energies.
• To determine the branching ratio of MgD+ and MgH+ formation.
• To assess the fragmentation probability of intermediate ionic complexes.

Main Methods:

• Single reaction event studies of Mg+ with HD, H2, and D2 at thermal energies.
• Quantitative analysis of product formation (MgD+, MgH+) and complex fragmentation.

Main Results:

• A branching ratio greater than 5 for MgD+ formation over MgH+ was observed in reactions with HD.
• The fragmentation probability of intermediate MgH2+, MgHD+, and MgD2+ complexes was found to be consistent across different isotopic compositions.
• Few single ion reactions can provide quantitative data on ion-neutral reactions.

Conclusions:

• Single ion reaction studies are effective for quantitative analysis of ion-neutral reactions, even with limited sample sizes.
• This method is highly suitable for studying rare isotopes and short-lived unstable elements.
• Isotope effects significantly influence the reaction pathways of Mg+ with molecular hydrogen.