Publication Date

Spring 2022

Degree Type


Degree Name

Master of Science (MS)


Physics and Astronomy


Thomas Madura

Subject Areas



Cosmic ices contain ions produced by irradiation from cosmic rays and UVphotons, yet solid-phase ion-ice reactions are currently ignored in all astrochemical models, even though gas-phase ion-molecule reactions are arguably the single-most important class of reactions in astrochemistry. Thus, developing a model that includes solid-phase ion-ice reactions is essential to accurately model interstellar ice chemistry, especially given the recent launch of the James Webb Space Telescope. To fill this gap, we have compiled a solid-phase chemical network for use in a rate-based irradiated ice astrochemical model which, for the first time, includes ionic species produced via the photoionization of the ice. Using this network, we simulated the photo-irradiation of a pure O2 ice and constrained the photolysis rates through direct comparison with experimental data. The fit of the model is in qualitative agreement with the experimental findings to give a general idea of what ionic chemistry occurs in irradiated ices. Our preliminary results indicate that ion-neutral chemistry contributes significantly more to solid phase reactivity than previously assumed. As in the gas-phase, solid-phase ion-ice reactions are very efficient and, indeed, become the dominant formation routes for the neutral species in our network.