Publication
Water is the solvent that enables life, essential to every biological process and shaping our environment. Yet, it is the most anomalous liquid known to humankind. Many of these anomalous properties originate from the deeply supercooled regime. Unfortunately, rapid crystallization at these temperatures has made it experimentally very challenging to access this region, earning it the nickname "no man's land" of water. This thesis aims to further our understanding of the thermodynamic properties of supercooled water as well as its crystallization kinetics by using time-resolved electron diffraction combined with laser heating cryogenic water samples.
Chapter 3 investigates water's structure during flash melting amorphous ice. Despite high heating rates of approximately 5 × 106 Ks-1, the sample transiently crystallizes, but revitrifies with similar cooling rates of 107 Ks-1 after the laser pulse. We further find, that hyperquenced glassy water crystallizes faster than amorphous solid water. These experiments provide insights into the crystallization mechanism of water and open up possibilities for studying its dynamics in no man's land.
The second study, chapter 4, investigates the vitrification of pure water. This process enables the cryo preservation of biological samples and is at the basis of cryoelectron microscopy. Due to the lack of direct measurements, the estimates of the critical cooling rate vary by orders of magnitude. Here, we use shaped laser pulses to systematically measure the vitrification of water at well defined rates. By following the structural evolution of water with time-resolved electron diffraction pattern we determine the critical cooling rate to be 6.4e6 K/s.
The last study in this thesis is outlined in chapter 5. H2O and D2O undergo a smooth structural transition from a room-temperature liquid water to vitreous ice. The position of the first diffraction maximum in D2O closely follows that of H2O but is shifted to higher temperatures, which suggests that for a given temperature D2O is more structured than H2O. Both liquids can be decomposed into low- and high-temperature components at all temperatures. Interestingly, for D2O the transition between the two components is not only at higher temperatures than H2O, but it is also narrower. These stark differences between the two isotopologues show that nuclear quantum effects play an important role in the phase behavior of water.
Our experiments further the understanding of the thermodynamics and kinetics of supercooled water, which is crucial for unraveling water's anomalous behavior. Additionally, they provide valuable insight into the emerging field of microsecond time-resolved cryo-EM, which holds great potential for advancing our comprehension of dynamic processes in molecular biology. The technique presented here is general and can be applied to investigate a wide range of interesting processes and properties.