Extremely Powerful X-ray Laser Heats Water to 180,000 Degrees in Less than a Trillionth of a Second

An international team of researchers has used a powerful X-ray laser to heat room-temperature water to 100,000 degrees Celsius (180,032 Fahrenheit) in less than a trillionth of a second.

The team’s experiments—which are described in a paper published in the journal Proceedings of the National Academy of Sciences—produced an exotic state of water, which may provide new insights into perhaps the most important substance on Earth.

Scientists from the Center for Free-Electron Laser Science (CFEL) and Uppsala University in Sweden used a laser known as the Linac Coherent Light Source (LCLS) at the SLAC National Accelerator Laboratory to shoot extremely intense but incredibly brief pulses of X-rays at a jet of water.

This rapidly heats the water but the effect is very different to normal boiling, according to Carl Caleman from CFEL.

"Normally, when you heat water, the molecules will just be shaken stronger and stronger,” he said in a statement.  "Our heating is fundamentally different. 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."

This meant that in less than 75 femtoseconds (75 millionths of a billionth of a second), the water changed state from a liquid to plasma—the fourth fundamental state of matter, that takes the form of an electrically charged gas where the electrons have been removed from the atoms.

As the water transforms from liquid to plasma, it remains at the density of liquid water because the atoms don’t have time to move significantly. In this state, the water exists in a form of matter that cannot be found naturally on Earth.

"It has similar characteristics as some plasmas in the sun and the gas giant Jupiter, but has a lower density,” Olof Jönsson from Uppsala University said in the statement. “Meanwhile, it is hotter than Earth's core."

image_thumbnail Screen shot of a simulation of water molecules and atoms in the first 70 femtoseconds of the intense X-ray pulse. Carl Caleman, CFEL/DESY and Uppsala University

The team’s research has cast new light on the properties of water, which are actually very peculiar, featuring many anomalies with regards to its density, heat capacity and thermal conductivity, among other characteristics.

For example, unlike almost any other known substance, water's solid form floats on its liquid form and water ice expands rather than contracting. It also has the highest surface tension of all known liquids. In addition, when it is super-cooled it may exist in two different states simultaneously—as recent research has demonstrated.

"Water really is an odd liquid, and if it weren't for its peculiar characteristics, many things on Earth wouldn't be as they are, particularly life," Jönsson said.

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