Desorption of neutrals, cations and anions from core-excited amorphous solid water

Abstract

Core-excitation of water ice releases many different molecules and ions in the gas phase. Studying these desorbed species and the underlying mechanisms can provide useful information on the effects of X-ray irradiation in ice. We report a detailed study of the X-ray induced desorption of a number of neutral, cationic and anionic species from amorphous solid water. We discuss the desorption mechanisms, and the relative contributions of Auger and secondary electrons (X-ray induced Electron Stimulated Desorption) and initial excitation (\rev{direct desorption}) as well as the role of photochemistry. Anions are shown to desorb not just through processes linked with secondary electrons but also through direct dissociation of the core-excited molecule. The desorption spectra of oxygen ions (O${}^{+}$, OH${}^{+}$, H${}_2$O${}^{+}$, O${}^{-}$, OH${}^{-}$) give a new perspective on their previously reported very low desorption yields for most types of irradiation of water, showing that they mostly originate from the dissociation of photoproducts such as H${}_2$O${}_2$.

arXiv commentAccepted in Journal of Chemical Physics

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• Indirect X-ray photodesorption of 15N2 and 13CO from mixed and layered ices