Anomales elastisches Verhalten von Eis bei tiefen Temperaturen

The temperature dependence of the longitudinal elastic constants of ice single crystals has been measured by an ultrasonic pulse-echo method. With heating, resp. cooling rates less than a critical value, deviations to lower values of the elastic constants have been observed. The time dependence of the anomaly has been studied at fixed temperatures. Limiting values of the elastic constants have been reached after sufficiently long time; the maximum of these values was observed at about 105°K. The findings are interpreted as representing a phase transition within the protonic structure.