Real-time latent heat emission during dynamic-compression freezing of water

The temperature of liquid water was measured during quasi-isentropic compression for the first time. Compression was achieved through multiple shock wave loading using sapphire windows, where photon Doppler velocimetry (PDV) was collected at the liquid/window interface and the radiance was simultaneously collected from a ZrF fiber on an amplified liquid nitrogen cooled InSb detector with ~10 ns time resolution. The results show ice clusters form at pressures below the previously defined metastable limit of 6 – 7 GPa for homogeneous nucleation of ice VII. We also show the water is not hypercoooled as previously described. Instead, the latent heat from solidification brings the temperature to the liquid-ice VII melt line, where it remains with increasing pressure. We suggest an alternative hypothesis to corroborate the results presented here with previous work on dynamic compression freezing of liquid water.