Cosmic ray sputtering yield of interstellar ice mantles

CO and CO₂ ice thickness dependence^★

¹ Institut des Sciences Moléculaires d’Orsay, UMR8214, CNRS, Université Paris-Saclay, 91405 Orsay, France
e-mail: emmanuel.dartois@universite-paris-saclay.fr
² Laboratoire de physique des deux infinis Irène Joliot-Curie, CNRS-IN2P3, Université Paris-Saclay, 91405 Orsay, France
³ Centre de Recherche sur les Ions, les Matériaux et la Photonique, CIMAP-CIRIL-GANIL, Normandie Université, ENSICAEN, UNICAEN, CEA, CNRS, 14000 Caen, France
⁴ Institut de planétologie et d’astrophysique de Grenoble, CNRS, Université Grenoble Alpes, 38000 Grenoble, France
⁵ Department of Physics, Indian Institute of Technology, Hauz Khas, New Delhi 110016, India

Received: 27 September 2020
Accepted: 22 January 2021

Abstract

Aims. Cosmic-ray-induced sputtering is one of the important desorption mechanisms at work in astrophysical environments. The chemical evolution observed in high-density regions, from dense clouds to protoplanetary disks, and the release of species condensed on dust grains, is one key parameter to be taken into account in interpretations of both observations and models.

Methods. This study is part of an ongoing systematic experimental determination of the parameters to consider in astrophysical cosmic ray sputtering. As was already done for water ice, we investigated the sputtering yield as a function of ice mantle thickness for the two next most abundant species of ice mantles, carbon monoxide and carbon dioxide, which were exposed to several ion beams to explore the dependence with deposited energy.

Results. These ice sputtering yields are constant for thick films. It decreases rapidly for thin ice films when reaching the impinging ion sputtering desorption depth. An ice mantle thickness dependence constraint can be implemented in the astrophysical modelling of the sputtering process, in particular close to the onset of ice mantle formation at low visual extinctions.