Thermal desorption characteristics of CO, O2 and CO2 on non-porous water, crystalline water and silicate surfaces at sub-monolayer and multilayer coverages

摘要

The desorption characteristics of molecules on interstellar dust grains areimportant for modelling the behaviour of molecules in icy mantles and,critically, in describing the solid-gas interface. In this study, a series oflaboratory experiments exploring the desorption of three small molecules fromthree astrophysically relevant surfaces are presented. The desorption of CO, O2and CO2 at both sub-monolayer and multilayer coverages was investigated fromnon-porous water, crystalline water and silicate surfaces. Experimental datawas modelled using the Polanyi-Wigner equation to produce a mathematicaldescription of the desorption of each molecular species from each type ofsurface, uniquely describing both the monolayer and multilayer desorption in asingle combined model. The implications of desorption behaviour overastrophysically relevant timescales are discussed.