Behavior of Hydroxyl Radicals on Water Ice at Low Temperatures

TL;DR

This study investigates the behavior of hydroxyl radicals on amorphous solid water ice at low temperatures to better understand radical-mediated chemistry relevant to interstellar molecular synthesis.

Contribution

It introduces a novel in situ detection method for OH radicals on water ice surfaces under astrophysical conditions.

Findings

OH radicals are highly reactive on water ice at low temperatures.

The new detection method allows real-time monitoring of radical reactions.

Results suggest radicals significantly influence astrochemical processes.

Abstract

Because chemical reactions on/in cosmic ice dust grains covered by amorphous solid water (ASW) play important roles in generating a variety of molecules, many experimental and theoretical studies have focused on the chemical processes occurring on the ASW surface. In laboratory experiments, conventional spectroscopic and mass-spectrometric detection of stable products is generally employed to deduce reaction channels and mechanisms. However, despite their importance, the details of chemical reactions involving reactive species (i.e., free radicals) have not been clarified because of the absence of experimental methods for in situ detection of radicals. Because OH radicals can be easily produced in interstellar conditions by not only the photolysis and/or ion bombardments of H2O but also the reaction of H and O atoms, they are thought to be one of the most abundant radicals on ice dust. In this context, the development of a close monitoring method of OH radicals on the ASW surface may help to elucidate the chemical reactions occurring on the ASW surface.