A sensitivity analysis of interstellar ice chemistry in astrochemical models

¹ Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, PO Box 9502, 2300 RA Leiden, The Netherlands
² Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
³ Institute for Molecules and Materials, Radboud University, 6525 AJ Nijmegen, The Netherlands
⁴ Transdisciplinary Research Area (TRA) ‘Matter’/Argelander-Institut für Astronomie, University of Bonn, 53121 Bonn, Germany
⁵ Department of Physics and Astronomy, University College London, Gower Street, London, UK

^★ Corresponding authors: This email address is being protected from spambots. You need JavaScript enabled to view it. ; This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 31 October 2025
Accepted: 8 December 2025

Abstract

Context. Astrochemical models are essential to bridging the gap between the timescales of reactions, experiments, and observations. The ice chemistry in these models is faced with a significant computational complexity given the many parameters required to modeling the chemical processes occurring on these ices, such as binding energies and reaction energy barriers. Many of these parameters are poorly constrained and attempting to accurately determine all of them would be too costly.

Aims. We aim to find out which specific parameters related to the ice chemistry have a large effect on the calculated abundances of ices for different prestellar objects.

Methods. 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 the UCLCHEM astrochemical modeling code on each of these parameters. We did this for a large grid of physical conditions across temperature, density, cosmic ray ionization rate, and UV field strength.

Results. Regardless of the physical conditions, the main sensitivities for the 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. Therefore, these parameters should be determined more accurately to increase the accuracy of models, paving the way to a better understanding of observations of interstellar ices. In many cases, accurate reaction energy barriers are not essential due to the competition between reactions and diffusion.