Spectroscopic measurements of ice XI

Inelastic incoherent neutron scattering from ice XI, the proton-ordered form of ice Ih, has been measured, and using Raman spectroscopy the transition to ice XI has been examined. The differences between the ice XI and ice Ih spectra are small in the molecular translational region, but much larger in the librational band, where the spectrum from ice XI is the more structured. The differences are greater when the momentum transfer is parallel rather than perpendicular to the c axis, suggesting that there is more ordering parallel to the c axis or that this ordering has a more significant effect on the librations.