Measurements and simulations of rate coefficients for the deuterated forms of the H2 + + H2 and H3 + + H2 reactive systems at low temperature

TL;DR

This study measured and simulated rate coefficients for deuterated H2+ and H3+ reactions at low temperatures, revealing implications for astrochemical models and deuteration processes in space.

Contribution

The paper provides new low-temperature rate coefficients for deuterated H2+ and H3+ reactions, including simulations that constrain unmeasured rates, improving astrochemical modeling accuracy.

Findings

Reactions with diatomic ions follow Langevin rate behavior.

Temperature-dependent rates were obtained for isotopic exchange processes.

Deuterated H3+ forms are more efficiently hydrogenated than previously assumed.

Abstract

The rate coefficients of various isotopic variations of the H2+ + H2 and H3+ + H2 reactions in the 10-250 K temperature range were measured using a cryogenic 22 pole radio frequency ion trap. The processes involving diatomic ions were found to behave close to the Langevin rate, whereas temperature-dependent rate coefficients were obtained for the four isotopic exchange processes with triatomic ions. Fitting the experimental data using a chemical code allowed us in specific cases to constrain rate coefficients that were not directly measured in the ion trap. The reported rate coefficients suggest a more efficient hydrogenation of deuterated H3+ forms than usually assumed in astrochemical models, which might affect deuteration rates in warmer environments.