Infrared Spectroscopy Of Clathrate Hydrates For Planetary Science: The Ethylene Case

Ethylene clathrate infrared spectra in the near infrared region involving combinations/overtones, recorded between 6K and 160K. Tentative assignments of the implied vibrational modes are given (see text for details). The crystalline pure ethylene spectrum of (Hudson et al. 2014) recorded at 16K is shown just above. A pure ethylene spectrum recorded in the cell at 77K is shown on top. Spectra are offset for clarity

Hydrocarbons are observed in the gas or solid phases of solar system objects, including comets, Trans-Neptunian Objects, planets and their moons. In the presence of water ice in these environments, hydrocarbons-bearing clathrate hydrates could form.

In clathrate hydrates, guest molecules are trapped in crystalline water cages of different sizes, a phase used in models of planetary (sub-)surfaces or icy bodies such as comets. The phases in presence, the potential estimate of abundances of hydrocarbon species, the spectroscopic behaviour of hydrocarbon species in the different phases must be recorded to provide reference spectra for the comparison with remote observations.

We show in this study the specific encaged ethylene signatures, with bands similar in position, but shifted from the pure ethylene ice spectrum. They show a marked temperature dependence both in position and width. Some vibrational modes are activated in the infrared by interaction with the water ice cages.

Emmanuel Dartois

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2104.07107 [astro-ph.EP] (or arXiv:2104.07107v1 [astro-ph.EP] for this version)
Submission history
From: Emmanuel Dartois
[v1] Wed, 14 Apr 2021 20:19:03 UTC (2,352 KB)
Astrobiology, Astrochemistry,

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