Enhanced production of HD and D_2 molecules on small dust grains in diffuse clouds

Abstract

Motivated by recent observations of deuterated molecules in the interstellar medium, we examine the production of HD and D${}_2$ molecules on dust grain surfaces. A mechanism for the enhanced production of these deuterated molecules is studied. This mechanism applies on grain surfaces on which D atoms stick more strongly than H atoms, under conditions of low flux and within a suitable range of temperatures. It is shown that under these conditions the production rates of HD and D${}_2$ are greatly enhanced (vs. the H${}_2$ production rate) compared with the expected rates based on the adsorption of gas-phase atomic abundances of D and H. The enhancement in the formation rate of HD is comparable with the enhancement due to gas-phase ion-molecule reactions in diffuse clouds.

arXiv commentThis is a preprint of an article accepted for publication in Monthly Notices of The Royal Astromnomical Society

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• Tracing early evolutionary stages of high-mass star formation with molecular lines
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• The D/H Ratio in the Interstellar Medium toward the White Dwarf PG0038+199
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• Monte Carlo simulation to investigate the formation of molecular hydrogen and its deuterated forms
• Molecular Hydrogen Formation During Dense Interstellar Cloud Collapse
• Low-temperature chemistry between water and hydroxyl radicals: H/D isotopic effects