How Cagey Electrons Keep Hydrated

December 20, 2007
How Cagey Electrons Keep Hydrated
Dennis Nordlund working at SSRL´s Beamline 5-2.

Water, despite its essential role in nature, remains a deeply mysterious substance. A long list of water's unusual properties tantalizes researchers even today, and scientists at the Stanford Synchrotron Radiation Laboratory (SSRL) and around the world are using x-rays to help address these questions. Working with SSRL scientist Anders Nilsson, researcher Dennis Nordlund and colleagues are turning up new clues, and their latest results are published in a recent issue of Physical Review Letters.

"Hydrated electrons" have been well-studied since the 1960s, and occur when free electrons become dissolved in water. Each water molecule is made up of two hydrogen atoms bound to an oxygen atom, and hydrated electrons form when a handful of water molecules congregate around a free electron, essentially trapping it in a cage of molecules.

Most agree that these cages consist of about six molecules. But the dynamics behind the process—how neighboring water molecules swing around, pointing one hydrogen atom inward to trap the electron—is not well understood.

Nordlund and colleagues, gathering data at Berkeley's Advanced Light Source and at MAX-Lab in Sweden, have for the first time measured how long an electron, having encountered a hydrogen atom of one water molecule, can stay in one place without hopping away, allowing other water molecules to swing into place and trap it.

Using x-rays to kick an electron free from an oxygen atom, in such a way that it remains close to its original water molecule, Nordlund’s group found that the electron is satisfied to wait about 20 femtoseconds before it hops away to interact with other molecules.

Although that’s inconceivably fast on a human timescale—a mere 20 quadrillionths of a second—that’s plenty long enough for the surrounding water molecules, all frenetically vibrating, to take notice of the free electron and move in to trap it.

"This is just one part of the puzzle," said Nordlund. "The final state of solvated electron and the overall timescale to get there is well-studied, but we don't know about what happens in between, like how the cages are formed, and on what timescale the initial part of the process occurs. This study adds to the information on the earliest stage, the actual trapping of the electron."

Knowing the timescales associated with how electrons become dissolved in water represents a further step toward creating a unified, precise model for describing the molecular behavior of water. At present, researchers must rely on a number of different molecular models to account for all of the strange properties of water. Unifying or replacing those models could impact society in ways at which today we may only guess—revolutionizing a range of fields from medicine to the search for alternative energy sources.

Source: by Brad Plummer, SLAC

Explore further: Rosetta shows how comet interacts with the solar wind

Related Stories

How to look for a few good catalysts

July 30, 2015

Two key physical phenomena take place at the surfaces of materials: catalysis and wetting. A catalyst enhances the rate of chemical reactions; wetting refers to how liquids spread across a surface.

Researchers build bacteria's photosynthetic engine

July 29, 2015

Nearly all life on Earth depends on photosynthesis, the conversion of light energy into chemical energy. Oxygen-producing plants and cyanobacteria perfected this process 2.7 billion years ago. But the first photosynthetic ...

Insights into catalytic converters

July 24, 2015

Modern catalytic converters for the treatment of exhaust gases in vehicles with a combustion engine have largely contributed to reducing of pollutant emissions. By oxidation or reduction, i.e. the donation or acceptance of ...

Recommended for you

Two spin liquids square off in an iron-based superconductor

August 5, 2015

Despite a quarter-century of research since the discovery of the first high-temperature superconductors, scientists still don't have a clear picture of how these materials are able to conduct electricity with no energy loss. ...

The resplendent inflexibility of the rainbow

August 4, 2015

Children often ask simple questions that make you wonder if you really understand your subject. An young acquaintance of mine named Collin wondered why the colors of the rainbow were always in the same order—red, orange, ...

New device converts DC electric field to terahertz radiation

August 4, 2015

Terahertz radiation, the no-man's land of the electromagnetic spectrum, has long stymied researchers. Optical technologies can finagle light in the shorter-wavelength visible and infrared range, while electromagnetic techniques ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.