Astrochemistry

A Sensitivity Analysis Of Interstellar Ice Chemistry In Astrochemical Models

By Keith Cowing

Status Report

astro-ph.GA

November 9, 2025

Filed under astro-ph.GA, astrochemistry, astronomy, ices, Interstellar, organic chemistry

A Sensitivity Analysis Of Interstellar Ice Chemistry In Astrochemical Models — Abundances (top) and correlation coefficients (bottom) of H₂O, CO, CO₂, CH₃OH, and NH₃ ices at T = 10 K, n_{H/_{= 105 cm⁻³, ζ = 1.3 × 10⁻¹⁷_s−1 and F_UV = 1 Habing. In top panels, the dashed pink line indicates the abundance using the nominal network, black lines indicate the individual samples, and light green is the log-average of all samples. In bottom subplots, the dashed gray line indicates perfectly uncorrelated parameters (r_RIN = 0), and the filled gray area indicates “weakly” correlated parameters (|r_RIN| < 0.4). The colored filled areas correspond to the 95% confidence intervals of the correlation coefficients. -- astro-ph.GA}}

Astrochemical models are essential to bridge the gap between the timescales of reactions, experiments, and observations.

Ice chemistry in these models experiences a large computational complexity as a result of the many parameters required for the modeling of chemistry occurring on these ices, such as binding energies and reaction energy barriers.

Many of these parameters are poorly constrained, and accurately determining all would be too costly. We aim to find out which parameters describing ice chemistry have a large effect on the calculated abundances of ices for different prestellar objects.

Using Monte Carlo sampled binding energies, diffusion barriers, desorption and diffusion prefactors, and reaction energy barriers, we determined the sensitivity of the abundances of the main ice species calculated with UCLCHEM, an astrochemical modeling code, on each of these parameters.

We do this for a large grid of physical conditions across temperature, density, cosmic ray ionization rate and UV field strength. We find that, regardless of the physical conditions, the main sensitivities of abundances of the main ice species are the diffusion barriers of small and relatively mobile reactive species such as H, N, O, HCO, and CH₃.

Thus, these parameters should be determined more accurately to increase the accuracy of models, paving the way to a better understanding of observations of ices. In many cases, accurate reaction energy barriers are not essential due to the treatment of competition between reactions and diffusion.

Tobias M. Dijkhuis, Thanja Lamberts, Serena Viti, Herma M. Cuppen

Comments: 16 pages, 8 figures, submitted to Astronomy and Astrophysics, comments are welcome!
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2511.01042 [astro-ph.GA] (or arXiv:2511.01042v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2511.01042
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Submission history
From: Tobias Dijkhuis
[v1] Sun, 2 Nov 2025 18:36:08 UTC (27,218 KB)
https://arxiv.org/abs/2511.01042

Astrobiology, Astrochemistry,

Keith Cowing

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) 🖖🏻

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