H bonds in astrophysical ices

We have studied, by infrared absorption spectroscopy, the profile (shape and peak position) of the OH dangling bond feature in pure porous amorphous solid water (ASW) and in mixtures of water with other species (CO, CO2, O2, N2, H2O2, CH4, SO2, and CH3OH) at 12–16 K. Furthermore, we have investigated the effects of ion and UV irradiation on the morphology/porosity of amorphous water ice. Thin films (about 0.25–1 μm) of porous amorphous water ice were irradiated with 200 keV H+, 30 keV He+, and 10.2 eV Lyman alpha photons at 12–16 K. We have found that the profile of the OH dangling bond feature depends on the mixture considered and that the intensity of the OH dangling bond feature decreases after irradiation. This latter result indicates that the porosity of amorphous water ice decreases after both ion and UV irradiation.