The process enabled them to heat water to 100,000 degrees celsius in just 75 femtoseconds, or 75 millionths of a billionth of a second.
As a result, the water was turned into a dense, electrically charged state known as plasma, similar to various extreme cosmic environments.
Researcher Olof Jönsson from Uppsala University in Sweden told Cosmos Magazine: “It has similar characteristics as some plasmas in the sun and the gas giant Jupiter, but has a lower density.
“Meanwhile, it is hotter than Earth’s core.”
The team’s technique, published in the Proceedings of the National Academy of Sciences journal, is a breakthrough for students keen to use X-rays to study the structure of liquids.
X-ray diffraction is an accepted technique for looking at the structure of crystals and other solids.
However, the latest research demonstrates that the technique will need to be altered when applied to liquids.
Co-author Kenneth Beyerlein from the Centre for Free-Electron Laser Science (CFEL) in Hamburg, Germany, said: “Any sample that you put into the X-ray beam will be destroyed in the way that we observed.
“If you analyse anything that is not a crystal, you have to consider this.”
Measurements showed that the water molecules barely responded to the X-ray laser for the first 25 femtoseconds.
But by 50 femtoseconds they were turning to plasma.
The change to an electrically charged gas is the key to the sudden heating, which is quite different to what happens in the average electric jug, explained Carl Caleman from the Deutsches Elektronen-Synchrotron, also in Hamburg.
Mr Jönsson said despite being common on Earth, water had unusual characteristics that make it interesting to study.
He added: “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.”