Water ice at low temperatures and pressures: New Raman results

Within the two types of experiments, both securing high sample’s purity, solid phases of water were studied in the region of low temperatures (above 8 K) and low pressure, conditions similar to the very upper atmosphere. Spectral features characterizing amorphous and crystalline H2O and D2O ices were recognized in both types of experiments. Careful analyses of the results discovered change of the slope in the temperature dependence of all deconvoluted bands at nearly 84 K for the first time. We attribute this observation to the ice XI ↔ Ih phase transition that was previously reported only for doped, not for pure water.