Neutron spectroscopy of ice viii in the region of 20–500 mev

Vibrational spectra of high-pressure phase ice VIII have been studied by inelastic neutron scattering over a wide energy transfer range, including external intermolecular and internal intramolecular modes up to 500 meV. It was clearly shown that the stretching intramolecular modes in ice VIII exhibit a narrow peak at an energy of 426 meV (or 3436 (Formula presented)), which is higher than observed in all other known ice phases. The width of the peak (∼20 meV or 161 (Formula presented)) is much narrower than for other forms of ice (e.g., ∼40 meV or 323 (Formula presented) for ice Ih), indicating a weak coupling between lattice and intramolecular stretching modes.