Effects of H2 coating of grains on depletion of molecular species

Abstract

Physical conditions in dense and cold regions of interstellar clouds favour the formation of ice mantles on the surfaces of interstellar grains. It is predicted that most of the gaseous species heavier than H2 or He will adsorb onto the grains and will disappear from the gas-phase, changing its chemistry, within 10^9/n_H years. Nonetheless, many molecules in molecular clouds are not completely depleted in timescales of 10^5 yr. Several speculative mechanisms have been proposed to explain why molecules stay in the gas phase, but up to now none are fully convincing. At the same time, these mechanisms are not mutually exclusive and we can still explore the effects of other possible processes. We speculate on the consequences of H2 coating of grains on the evaporation rates of adsorbed species. More experiments and simulations are needed to calculate the evaporation rate Eevap(X-H2).

6 pages, 1 figure. Accepted for publication by MNRAS

References in corpus (6)

• Complex Chemistry in Star-Forming Regions: An Expanded Gas-Grain Warm-up Chemical Model
• Simulation of the Formation and Morphology of Ice Mantles on Interstellar Grains
• Desorption From Interstellar Ices
• Monte Carlo simulations of H2 formation on stochastically heated grains
• Beyond the pseudo-time-dependent approach: chemical models of dense core precursors
• Chemistry of dense clumps near moving Herbig-Haro objects

Cited by in corpus (3)

• A New and Simple Approach to Determine the Abundance of Hydrogen Molecules on Interstellar Ice Mantles
• On the Encounter Desorption of Hydrogen Atoms on Ice Mantle
• A sensitivity analysis of interstellar ice chemistry in astrochemical models