Vibrational dynamics of amorphous ice

Using inelastic neutron scattering, we have measured a range of amorphous forms of ice, including high-density and low-density amorphous ices, in the energy transfer region from 2 to 500 meV (16--4033 cm^-1). The measured spectra show that the pressure-produced high-density amorphous ice is significantly different from the two low-density amorphous forms of ice (obtained by vapor deposition and by annealing at 120 K of the high-density amorphous ice), as we expected. However, considerable differences were also observed between the vapor deposits and the low-density amorphous ice obtained from annealing the high-density amorphous ice (the latter has a spectrum very similar to ice-Ih and ice-Ic), indicating that the hydrogen bonding in the two systems are markedly different.