Such a rotation interchanges some of the molecule's protons and electron pairs. The electrical conduction in ice is carried by the protons, whose motion is closely tied to the motion of ionic defects. Protonic conduction plays a major role in biological charge transfer processes across membranes. Proton conduction in ice and H-bonded materials is analogous to electron conduction in semiconductors. The reorientation of the molecular dipoles in ice is facilitated by the mobility of orientational L and D defects, which are generated by thermal activation.
Ice is transparent to visible light.
It has the lowest index of refraction for the sodium D line of any known crystalline material. It is doubly refracting, uniaxial, optically positive with very small birefringence. Ih is centered around 840 cm -1 . The proton-ordered phases show distinct narrow peaks in their infrared and Raman spectra. From infrared and Raman spectroscopy on the ice phases, much has been learned about the intermolecular coupling mechanism, lattice dynamics, and the properties of H-bonds.