Kinetic Monte Carlo simulations of the grain-surface back-diffusion effect

Abstract

Back-diffusion is the phenomenon by which random walkers revisit binding sites on a lattice. This phenomenon must occur on interstellar dust particles, slowing down dust-grain reactions, but it is not accounted for by standard rate-equation models. Microscopic kinetic Monte Carlo models have been used to investigate the effect of back-diffusion on reaction rates on interstellar dust grains. Grain morphology, size, and grain-surface coverage were varied and the effects of these variations on the magnitude of the back-diffusion effect were studied for the simple H+H reaction system. This back-diffusion effect is seen to reduce reaction rates by a maximum factor of ~5 for the canonical grain of 10${}^6$ binding sites.The resulting data were fit to logarithmic functions that can be used to reproduce the effects of back-diffusion in rate-equation models.

To appear in "Astrochemistry VII - Through the Cosmos from Galaxies to Planets," conference proceedings for IAU Symposium 332 in Puerto Varas, Chile (4 pages, 2 figures)

References in corpus (3)

• Three-dimensional off-lattice Monte Carlo kinetics simulations of interstellar grain chemistry and ice structure
• Molecular reordering processes on ice (0001) surfaces from long timescale simulations
• Diffusion-limited reactions and mortal random walkers in confined geometries