DESY Facility in Germany
(Photo : Maria Anna van Driel via Wikimedia Commons)

While investigating how water heats up under extreme conditions, a team of researchers observed water that remained in its liquid form even at 170 degrees Celsius—338 degrees Fahrenheit—and above.

Using the European X-Ray Free-Electron Laser (XFEL) facility, researchers with the  Deutsches Elektronen-Synchrotron (DESY) were able to identify this anomalous dynamic behavior of water. Their study, published in the journal Proceedings of the National Academy of Sciences (PNAS) on Tuesday, September 15.


Another Anomaly in Water

Researchers used a series of 120 X-ray laser flashes, with individual flashes 0.886 microseconds apart from each other. This pulsing X-ray laser is sent through a thin, quartz glass tube filled with water and observed its behavior.

"We asked ourselves how long and how strongly water can be heated in the X-ray laser and whether it still behaves like water," said Felix Lehmkühler, lead author of the study from DESY. German national research center Lehmkühler inquired, for example, if water could still function as a coolant under high temperatures. He stressed that investigating superheated water can help scientists understand its behavior, especially with temperature-sensitive applications like biological samples and polymers.

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As the X-ray laser pulses pass through the water sample, it heats the water up to temperatures of 172 degrees Celsius—341.6 degrees Fahrenheit. In the experimental setup, water reaches these temperatures within ten-thousandths of a second without it evaporating. Under standard conditions, this boiling delay has only been observed for up to 110 degrees Celsius—230 degrees Fahrenheit.

However, Lehmkühler notes that this evaporation delay is not the only anomalous behavior they have observed in the study. Within the water-filled quartz container also contained silicon nanospheres intended to be the markers for water dynamics.

"In the extremely overheated water, we observed that the movement of silicon dioxide nanospheres deviated significantly from the expected random Brownian molecular movement," the lead author described. This observation, according to Lehmkühler, is an indication of uneven heating of the water sample.

European XFEL Facility

Adrian Mancuso, a co-author of the study and head of the Single Particles, Clusters, and Biomolecules & Serial Femtosecond Crystallography (SPB/SFX), notes that the high repetition rate makes the European XFEL unique, referring to the frequency of its pulses. Mancuso also noted the presence of other specialized equipment that made experiments such as the recent study about the dynamic anomaly in water.

The European XFEL is an international research facility commissioned in 2017. Its 2.1-mile, or 3.4-kilometer, long tunnel houses its superconducting linear accelerator and photon beamlines. These are located 20 to 125 feet underground, from the DESY research site in Hamburg running to the town of Schenefeld in Schleswig-Holstein, both in Germany. The Schenefeld site also houses additional experimental stations, labs, and administrative buildings.

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Aside from generating the 170 degree Celsius superheated water, the XFEL setup also allowed the research team to conduct precisely controlled experiments with X-ray flashes of varying light intensity. Lehmkühler reported that through the use of silicon filters, they were able to control how much energy was used and how much heat was applied to the water.

Check out more news and information on Thermodynamics on Science Times.