Getting beneath the surface of water

Abstract

It may be everywhere, but there’s plenty that scientists don’t yet understand about water’s properties at the atomic scale. A group of researchers has made the first direct observation of how the atoms within water molecules move when excited—a finding that may lead to a more accurate picture of how energy flows during chemical reactions ( Nature 2021, DOI: 10.1038/s41586-021-03793-9 ). The researchers used the mega-electron-volt ultrafast electron diffraction instrument at SLAC National Accelerator Laboratory to capture the motion of molecular bonds within the water. They started with jets of water 100 nm thick, excited them with infrared laser light, and then fired bursts of high-energy electrons from the instrument into the stream to detect the vibrations. The team found that when a water molecule starts to vibrate, its hydrogen atom initially pulls the oxygen atoms in neighboring molecules toward it. Then, as the system heats up, the atoms move