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

TL;DR

This study investigates how CO, O2, and CO2 molecules desorb from various astrophysical surfaces, providing a comprehensive model of their behavior at different coverages to improve understanding of icy mantles on interstellar dust.

Contribution

It presents new laboratory data and a unified model describing the desorption of molecules from water and silicate surfaces relevant to astrophysics.

Findings

Desorption behavior varies significantly between surface types.

A combined model accurately describes monolayer and multilayer desorption.

Implications for molecular lifetimes in interstellar environments.

Abstract

The desorption characteristics of molecules on interstellar dust grains are important for modelling the behaviour of molecules in icy mantles and, critically, in describing the solid-gas interface. In this study, a series of laboratory experiments exploring the desorption of three small molecules from three astrophysically relevant surfaces are presented. The desorption of CO, O2 and CO2 at both sub-monolayer and multilayer coverages was investigated from non-porous water, crystalline water and silicate surfaces. Experimental data was modelled using the Polanyi-Wigner equation to produce a mathematical description of the desorption of each molecular species from each type of surface, uniquely describing both the monolayer and multilayer desorption in a single combined model. The implications of desorption behaviour over astrophysically relevant timescales are discussed.