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

  • Eric R. Willis (a1) and Robin T. Garrod (a1) (a2)

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 106 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.

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References

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Chang, Q., Cuppen, H. M., & Herbst, E., 2005, A&A, 434, 599
Garrod, R. T., 2008, A&A, 491, 239
Garrod, R. T., 2013, ApJ, 778, 158
Lohmar, I. & Krug, J., 2009, J. Stat. Phys., 134, 307
Pedersen, A., Wikfeldt, K. T., Karssemeijer, L., Cuppen, H., & Jónsson, H., 2014, J. Chem. Phys., 141, 234706
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Kinetic Monte Carlo simulations of the grain-surface back-diffusion effect

  • Eric R. Willis (a1) and Robin T. Garrod (a1) (a2)

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