The Effects of Subsurface Chemistry in the Grain Mantles on the Deuterium Chemistry in Molecular Clouds

Juris Kalvans, Ivar Shmeld
(Submitted on 15 Mar 2018)

The deuterium enrichment in molecules in dark molecular cloud cores and starforming regions is usually attributed to gas-phase chemistry. Here we examine the effects of surface and mantle chemical reactions on the deuteration of species. We use a simple kinetic chemistry model that includes gas, surface and mantle pore phase reactions of deuterated species. The mantle is assumed to be partially reactive due to pores with sufficient surface area for chemical reactions, that are continuously transformed by cosmic-rays. Calculation results show that surface reactions generally enhance the deuteration for at least several molecules. However, once they are buried and become mantle molecules, they lose their deuteration over a timescale of 10 million years due to processes in the mantle. If deuterated species in young star-forming regions come from grain mantles, a cautious conclusion is that the freeze-out of molecules, perhaps, should not occur more than 10 Myr before the mantle evaporates to the gas phase.

Comments:    Unpublished paper for Poster No. II.48 in IAUS 280 “The Molecular Universe” (2011). 6 pages, 2 figures
Subjects:    Astrophysics of Galaxies (astro-ph.GA)
Cite as:    arXiv:1803.05731 [astro-ph.GA] (or arXiv:1803.05731v1 [astro-ph.GA] for this version)
Submission history
From: Juris Kalvans Dr.phys.
[v1] Thu, 15 Mar 2018 13:21:53 GMT (65kb)
https://arxiv.org/abs/1803.05731
Astrobiology
Astrochemistry