FURTHER EVIDENCE FOR THE EXISTENCE OF 2 KINDS OF H-BONDS IN ICE IH

The hydrogen defects in the host D2O lattice of ice have been studied using a high resolution inelastic neutron spectrometer. Three main peaks at approximately 105, approximately 185 and approximately 408 meV, associated with three localised modes (mu1, mu2 and mu3) of the H-defect centre, have been observed in the inelastic neutron spectra. The peak associated with the mu1 mode at approximately 105 meV has an asymmetrical shape from which two Gaussian components centred at 103 +/- 0.5 and 107 +/- 0.5 meV for different concentrations of HDO can be resolved, confirming the existence of two different strengths for the H-bonds. A lattice dynamic calculation for the H defects in a perfect ice Ih lattice, based on the two H-bond force constants model of Li and Ross [Nature 365 (1993) 327], shows the three modes in very similar positions to those observed in the measured data and predicts the splitting of the mu1 peak into modes at 103 and 107 meV.