Glycolaldehyde Formation Mediated By Interstellar Amorphous Ice: A Computational Study

By Keith Cowing
Status Report
February 7, 2023
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Glycolaldehyde Formation Mediated By Interstellar Amorphous Ice: A Computational Study
Comparison between the proposed mechanism in the gas phase and on the surface of amorphous ice. The displayed energy of the solid phase is the average of the energies of the ten surfaces studied. All energies are at DFT level. — astro-ph.GA

Glycolaldehyde (HOCH2CHO) is the most straightforward sugar detected in the Interstellar Medium (ISM) and participates in the formation pathways of molecules fundamental to life, red such as ribose and derivatives.

Although detected in several regions of the ISM, its formation route is still debated and its abundance cannot be explained only by reactions in the gas phase. This work explores a new gas-phase formation mechanism for glycolaldehyde and compares the energy barrier reduction when the same route happens on the surface of amorphous ices.

The first step of the mechanism involves the formation of a carbon-carbon bond between formaldehyde (H2CO) and the formyl radical (HCO), with an energy barrier of 27 kJ mol-1 (gas-phase). The second step consists of barrierless hydrogen addition. Density functional calculations under periodic boundary conditions were applied to study this reaction path on 10 different amorphous ice surfaces through an Eley-Rideal type mechanism.

It was found that the energy barrier is reduced on average by 49 per cent, leading in some cases to a 100 per cent reduction. The calculated adsorption energy of glycolaldehyde suggests that it can be promptly desorbed to the gas phase after its formation.

This work, thus contributes to explaining the detected relative abundances of glycolaldehyde and opens a new methodological framework for studying the formation routes for Complex Organic Molecules (COMs) in interstellar icy grains.

Mateus A. M. Paiva, Sergio Pilling, Edgar Mendoza, Breno R. L. Galvão, Heitor A. De Abreu

Comments: 10 pages, 9 figures, supplementary data. Accepted for publication in Monthly Notices of the Royal Astronomical Society
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2302.02021 [astro-ph.GA] (or arXiv:2302.02021v1 [astro-ph.GA] for this version)
Journal reference: Monthly Notices of the Royal Astronomical Society, 2023, 519, 2518-2527
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Submission history
From: Edgar Mendoza
[v1] Fri, 3 Feb 2023 22:50:10 UTC (1,794 KB)
Astrobiology, Astrochemistry

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻