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

Max Planck Institute for Extraterrestrial Physics, Gießenbachstraße 1, 85748 Garching, Germany

^★ Corresponding author; pjusko@mpe.mpg.de

Received: 1 August 2024
Accepted: 4 November 2024

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.