It is remarkable that the physics of water, the substance that covers two thirds of our planet, is still not fully understood. This holds true especially also for its anomalous properties compared to other liquids.
Our research aims at the understanding of the anomalies of water, in particular those observed in the supercooled metastable state. To achieve this goal, pure water inclusions inside quartz are synthesized covering a density range of 996-916 kg m-3. Microthermometric measurements are conducted to determine the temperature at which water phase transitions occur. Single ultrashort (femtosecond) laser pulses are employed to overcome metastable phase states in high density inclusions. In pure water inclusions, the phase transition from liquid to solid is not visible from microscopic observations, thus, confocal Raman spectroscopy is used to determine ice nucleation temperatures. In addition, we use Brillouin spectroscopy to determine the speed of sound and, thus, the pressures inside the inclusions.
The experimental outcomes present valuable benchmarks to evaluate and further improve theoretical models describing the p–V–T properties of metastable water in the low-temperature region.