Regular Article – Molecular Physics and Chemical Physics
Laboratory experiments on the radiation astrochemistry of water ice phases
Centre for Astrophysics and Planetary Science, School of Physical Sciences, University of Kent, CT2 7NH, Canterbury, UK
2 Atomic and Molecular Physics Laboratory, Institute for Nuclear Research (Atomki), 4026, Debrecen, Hungary
3 School of Electronic Engineering and Computer Science, Queen Mary University of London, E1 4NS, London, UK
4 Astronomical Institute, Slovak Academy of Sciences, 059 60, Tatranská Lomnica, Slovak Republic
5 Department of Physics and Astronomy, School of Mathematics and Physics, Queen’s University Belfast, BT7 1NN, Belfast, UK
6 Department of Physics, Faculty of Mechanical Engineering and Informatics, University of Miskolc, 3515, Miskolc, Hungary
Accepted: 5 May 2022
Published online: 17 May 2022
Water (H2O) ice is a ubiquitous component of the universe, having been detected in a variety of interstellar and Solar System environments where radiation plays an important role in its physico-chemical transformations. Although the radiation chemistry of H2O astrophysical ice analogues has been well studied, direct and systematic comparisons of different solid phases are scarce and are typically limited to just two phases. In this article, we describe the results of an in-depth study of the 2 keV electron irradiation of amorphous solid water (ASW), restrained amorphous ice (RAI) and the cubic (Ic) and hexagonal (Ih) crystalline phases at 20 K so as to further uncover any potential dependence of the radiation physics and chemistry on the solid phase of the ice. Mid-infrared spectroscopic analysis of the four investigated H2O ice phases revealed that electron irradiation of the RAI, Ic, and Ih phases resulted in their amorphization (with the latter undergoing the process more slowly) while ASW underwent compaction. The abundance of hydrogen peroxide (H2O2) produced as a result of the irradiation was also found to vary between phases, with yields being highest in irradiated ASW. This observation is the cumulative result of several factors including the increased porosity and quantity of lattice defects in ASW, as well as its less extensive hydrogen-bonding network. Our results have astrophysical implications, particularly with regards to H2O-rich icy interstellar and Solar System bodies exposed to both radiation fields and temperature gradients.
© The Author(s) 2022
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.