Superheated ice

Ice single crystals are superheated by a pressure jump. Their optical homogeneity is examined by elastic light scattering in order to obtain information about the thermodynamic state in the bulk of the sample. The intensity of the scattered light after the pressure jump remains first unchanged. Only after a time lag a steep intensity increase is observed. The dependence of on the superheating, on sample size, on the position of the scattering volume in the sample, on crystal orientation, on the scattering angle and on the crystal quality is examined. depends only on superheating and crystal quality within experimental sensitivity. After a superheating of more than 5°C the optical appearance of ice is like opalescent glass. The observations are compatible with the assumption that the ice has been superheated with respect to the melt and that homogeneous nucleation occurs in the metastable state. The equilibrium curve iceI _h —water has been determined.