Diffusion-desorption ratio of adsorbed CO and CO$_2$ on water ice

TL;DR

This paper provides key data on the ratio of diffusion to desorption energy barriers for CO and CO$_2$ on water ice, crucial for improving astrochemical models of star-forming regions.

Contribution

It introduces a fully atomistic kinetic Monte Carlo method to accurately determine diffusion/desorption ratios for CO and CO$_2$ on water ice surfaces.

Findings

Diffusion/desorption ratio for CO is 0.31.

Diffusion/desorption ratio for CO$_2$ is 0.39.

Results can enhance the accuracy of astrochemical models.

Abstract

Diffusion of atoms and molecules is a key process for the chemical evolution in the star forming regions of the interstellar medium. Accurate data on the mobility of many important interstellar species is however often not available and this provides a serious limitation for the reliability of models describing the physical and chemical processes in molecular clouds. Here we aim to provide the astrochemical modeling community with reliable data on the ratio between the energy barriers for diffusion and desorption for adsorbed CO and CO$_2$ on water ices. To this end, we use a fully atomistic, off-lattice kinetic Monte Carlo technique to generate dynamical trajectories of CO and CO$_2$ molecules on the surface of crystalline ice at temperatures relevant for the interstellar medium. The diffusion to desorption barrier ratios are determined to be 0.31 for CO and 0.39 for CO$_2$ . These ratios can be directly used to improve the accuracy of current gas-grain chemical models.