New Insights into Hydrated Electrons

Sep 23, 2004
New Insights into Hydrated Electrons

Sometimes, it pays to think small. By observing how a single electron behaves amid a cluster of water molecules, a team of scientists has gained a better understanding of a fundamental process that drives a myriad of biological and chemical phenomena, such as the formation of reactive molecules in the body that can cause disease.

The researchers, led by Lawrence Berkeley National Laboratory’s Chemical Sciences Division Director Daniel Neumark, used an extremely fast imaging technique to observe an excited electron, surrounded by several dozen water molecules, relax back to its original energy state. This journey occurred much more quickly than one theory predicts, lending credence to an opposing theory and helping to solve a longstanding puzzle in the world of hydrated electrons.

“Our work tells us something very basic about the nature of the interactions between electrons and water, which is of general, cross-cutting interest to many scientists,” says Neumark, who conducted the study with scientists from the University of California at Berkeley and Israel’s Tel-Aviv University. Their research is published in the September 16, 2004 edition of Science Express.

As their name implies, hydrated electrons are electrons that are dissolved in water. They occupy an elliptical void formed by six water molecules, and they’ve intrigued scientists since their discovery in 1962. The simple fact that they exist is interesting, as is their little understood role in many biological and chemical processes. Although it is too early to tell how Neumark’s work will elucidate the behavior of hydrated electrons in the real world, such as how they conspire to form free radicals (highly reactive molecules that can damage tissue and contribute to diseases such as cancer, rheumatoid arthritis, and heart disease), it will help shape future research.

Leading up to this study, scientists had been divided as to how hydrated electrons react after they’ve been excited. One theory holds that electrons convert back to their original energy state in about 50 femtoseconds, or 50 millionths of a billionth of a second. The other theory contends this conversion takes much longer, about 500 femtoseconds.

Most research into this phenomenon has explored the behavior of hydrated electrons in a large quantity of water, called a bulk. Bulk experiments can yield very precise measurements, but they have trouble portraying the various components of the electrons’ journey between energy states. To get a more precise look, Neumark’s team instead observed a single electron in a tiny cluster of between 25 and 50 water molecules. Such clusters give scientists an extremely close look at the electron’s dynamics. For example, they can determine whether water molecules are simply rearranging themselves around an electron in an excited or a ground state, or whether these dynamics indicate the actual transition of the electron between these states.

The team created an electronic excitation by zapping the cluster with a femtosecond laser pulse. They then used time-resolved photoelectron imaging to take snapshots of the electron as it relaxed back to its ground state. The dynamics and rate of this conversion, when extrapolated to how hydrated electrons behave in bulk, suggest that hydrated electrons relax back to their unexcited state in about 50 femtoseconds — a finding that tips the scales in favor of this theory.

“Resolving which of these two models is correct is a key step. We’ve used time-resolved studies of finite clusters to resolve an issue of fundamental importance, namely the dynamics of an excited hydrated electron,” says Neumark. “More generally, this work represents a fairly unique example of how studies of clusters can elucidate bulk phenomena.”

This research is supported in part by the National Science Foundation.

Source: Berkeley Lab

Explore further: 'Comb on a chip' powers new atomic clock design

add to favorites email to friend print save as pdf

Related Stories

Water molecules favor negative charges

Jul 16, 2014

( —In the presence of charged substances, H2O molecules favor associating with elements with a negative electrical charge rather than a positive electric charge. EPFL researchers have published ...

Researchers team up on potential fuel cell advance

Dec 19, 2013

Scientists at SLAC National Accelerator Laboratory put together clues from experiments and theory to discover subtle variations in the way fuel cells generate electricity – an advance that could lead to ...

Robots may receive urine-powered artificial 'hearts'

Nov 27, 2013

( —It's a first: researchers have built the first artificial-heart-like pump that is powered by microbial fuel cells fed on human urine. But instead of being used as a prosthetic device for human ...

In water as in love, likes can attract

Sep 19, 2013

( —At some point in elementary school you were shown that opposite charges attract and like charges repel. This is a universal scientific truth – except when it isn't. A research team led by ...

Recommended for you

'Comb on a chip' powers new atomic clock design

6 hours ago

Researchers from the National Institute of Standards and Technology (NIST) and California Institute of Technology (Caltech) have demonstrated a new design for an atomic clock that is based on a chip-scale ...

Quantum leap in lasers brightens future for quantum computing

6 hours ago

Dartmouth scientists and their colleagues have devised a breakthrough laser that uses a single artificial atom to generate and emit particles of light. The laser may play a crucial role in the development of quantum computers, ...

Technique simplifies the creation of high-tech crystals

6 hours ago

Highly purified crystals that split light with uncanny precision are key parts of high-powered lenses, specialized optics and, potentially, computers that manipulate light instead of electricity. But producing ...

A new multi-bit 'spin' for MRAM storage

9 hours ago

Interest in magnetic random access memory (MRAM) is escalating, thanks to demand for fast, low-cost, nonvolatile, low-consumption, secure memory devices. MRAM, which relies on manipulating the magnetization ...

User comments : 0