Inelastic incoherent neutron scattering study of ice Ih, II, IX, V and VI in the region from 50-500 meV

Abstract

Inelastic incoherent neutron scattering spectra of ice Ih and recovered high-pressure ice II, IX, V and VI were measured in the range of energy transfer from 50 to 500 meV at 20 K using the high-energy transfer (HET) spectrometer at ISIS. The excellent resolution and large-Q range of this instrument enable the authors to examine the vibration modes of these ices in great detail. The results clearly show that the low-energy cut-offs of the librational bands shift towards lower energy transfers by amounts ranging from 4 meV for ice IX to 12 meV for ice VI as compared with ice Ih. There is no clear high-energy cut-off for this band for ice V and VI. For the intramolecular stretching modes, the main peak at about 414 meV for ice Ih is shifted towards higher energy transfer for these recovered ices while there is no clear evidence of any shift in the intramolecular bending modes at about 200 meV.