Scientists have used a powerful X-ray laser to heat water from room temperature to 100,000 degrees Celsius in less than a tenth of a picosecond (millionth of a millionth of a second). The experimental set-up, that can be seen as the world's fastest water heater, produced an exotic state of water, from which researchers hope to learn more about the peculiar characteristics of Earth's most important liquid. The observations also have practical use for the probing biological and many other samples with X-ray lasers. The team of Carl Caleman from the Center for Free-Electron Laser Science (CFEL) at DESY and Uppsala University (Sweden) reports its findings in the journal Proceedings of the National Academy of Sciences (PNAS).
The researchers used the X-ray free-electron laser Linac Coherent Light Source LCLS at the SLAC National Accelerator Laboratory in the U.S. to shoot extremely intense and ultra-short flashes of X-rays at a jet of water. On the molecular level, heat is motion the hotter, the faster the motion of the molecules. This can be achieved, for example, via heat transfer from a stove, or more directly with microwaves that make the water molecules swing back and forth ever faster in step with the electromagnetic field.
The energetic X-rays punch electrons out of the water molecules, thereby destroying the balance of electric charges. So, suddenly the atoms feel a strong repulsive force and start to move violently." In less than 75 femtoseconds, that's 75 millionths of a billionth of a second or 0.000 000 000 000 075 seconds, the water goes through a phase transition from liquid to plasma. A plasma is a state of matter where the electrons have been removed from the atoms, leading to a sort of electrically charged gas.