Inelastic neutron scattering study of high density amorphous water ice

Abstract

The various forms of amorphous ices with trapped impurities play an important role in astrophysics. Such ices observed spectroscopically as frost on interstellar dust in dense molecular clouds and in comets require a detailed understanding of the spectroscopic properties in laboratory conditions. Using the neutron inelastic scattering technique on ISIS at Rutherford-Appleton Laboratory, the recovered high density amorphous ice is measured along with its subsequent high temperature metastable phases: low density amorphous ice, cubic and hexagonal ices under the same conditions in the energy transfer region from 2 to 500 meV (i.e. 16–4025 cm −1). The results show that the spectra of low density amorphous ice have similar features to cubic and hexagonal ices. However, the spectrum for the high density amorphous ice is significantly different from the others in the translational and librational regions (< 150 meV).