Dynamics of CO in Amorphous Water Ice Environments

Abstract

The long-timescale behavior of adsorbed carbon monoxide on the surface of amorphous water ice is studied under dense cloud conditions by means of off-lattice, on-the-fly, kinetic Monte Carlo simula- tions. It is found that the CO mobility is strongly influenced by the morphology of the ice substrate. Nanopores on the surface provide strong binding sites which can effectively immobilize the adsorbates at low coverage. As the coverage increases, these strong binding sites are gradually occupied leav- ing a number of admolecules with the ability to diffuse over the surface. Binding energies, and the energy barrier for diffusion are extracted for various coverages. Additionally, the mobility of CO is determined from isothermal desorption experiments. Reasonable agreement on the diffusivity of CO is found with the simulations. Analysis of the 2152 cm${}^{-1}$, polar CO band supports the computational findings that the pores in the water ice provide the strongest binding sites and dominate diffusion at low temperatures.

16 pages, 9 figures, Published in ApJ

References in corpus (4)

• Complex Chemistry in Star-Forming Regions: An Expanded Gas-Grain Warm-up Chemical Model
• Spatial mapping of ices in the Oph-F core: A direct measurement of CO depletion and the formation of CO2
• Mobility of D atoms on porous amorphous water ice surfaces under interstellar conditions
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