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Laboratory Experiments on the Radiation Astrochemistry of Water Ice Phases

Laboratory Experiments on the Radiation Astrochemistry of Water Ice Phases

Water ice (H2O) 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 the astrophysical analogues of H2O ice has been well studied, direct and systematic comparisons of the different solid phases are rare and usually limited to only two phases. In this paper, we describe the results of an extensive study of the 2 keV electron irradiation of amorphous solid water (ASW), retained amorphous ice (RAI), and cubic (Ic) and hexagonal ( Ih) at 20 K to further uncover any potential dependence of radiation physics and chemistry on the solid phase of ice. Mid-infrared spectroscopic analysis of the four studied H2O ice phases revealed that electron irradiation of the RAI, Ic and Ih phases resulted in their amorphization (the latter undergoing the process more slowly) while the ASW underwent compaction .

The abundance of hydrogen peroxide (H2O2) produced as a result of 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 amount of lattice defects in ASW, as well as its less extensive hydrogen bonding lattice. Our findings have astrophysical implications, particularly with respect to H2O-rich icy interstellar and solar bodies exposed to both radiation fields and temperature gradients.

Duncan V. Mifsud, Perry A. Hailey, Péter Herczku, Zoltán Juhász, Sándor TS Kovács, Béla Sulik, Sergio Ioppolo, Zuzana Kaňuchová, Robert W. McCullough, Béla Paripás, Nigel J. Mason

Comments: Published in the European Physical Journal D: Atomic, Molecular, Optical, and Plasma Physics
Subjects: Astrophysics of Galaxies (astro-ph.GA); Terrestrial and planetary astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Other condensed matter (cond-mat.other)
Cite as: arXiv:2206.11614 [astro-ph.GA] (or arXiv:2206.11614v1 [astro-ph.GA] for this version)
Journal reference: Eur. Phys. JD 76, 87 (2022)
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Submission History
By: Duncan V. Mifsud
[v1] Thu, Jun 23, 2022 10:47:36 AM UTC (1,076 KB)
Astrobiology, Astrochemistry,