January 27, 2010
Chemistry professors Stephen Leone and Daniel Neumark have won a $1 million grant to help establish an attosecond science laboratory in the College of Chemistry. The award is one of two grants, each worth one million dollars, made to the Berkeley campus recently by the W. M. Keck Foundation. The other grant was awarded to mechanical engineering professor Lydia Sohn and colleagues.
The new attosecond science lab will probe the dynamics of electron movement over the timeframe of attoseconds (10-18 seconds), with particular application to solid state nanomaterials. Says Leone, “This grant comes at a critical time and will help set up a lab for experiments that currently cannot be done anywhere else in the world.”
Just as we have gained tremendous insights from more and more powerful microscopes, so we gain knowledge by zooming in on shorter and shorter time scales. It wasn’t until the late 1800s that millisecond imaging evolved to the point it could answer a question that had vexed many generations—when a horse gallops, are all four feet ever off the ground at the same time?
With the development of cameras and films that were capable of creating images at shutter speeds of around one millisecond (10-3 seconds), the question was finally resolved. The images showed that horses did have all four feet off the ground at one moment during their stride.
“Today,” says Leone, “we are pushing the limits of high speed dynamics. Electrons are one of our modern workhorses, and for many applications, we need to understand how they move. The problem is that electrons move much faster than horses’ legs. Millisecond imaging was good enough to understand horses. To understand electrons, we need attosecond science, or the ability to trace how electrons move in a few hundred billion billionths of a second.”
Leone and Neumark are experts in chemical and physical dynamics, fields that probe how movements of molecules and electrons take place in real time. “Attosecond science represents the next frontier in atomic, molecular, and chemical physics,” says Neumark. “Attosecond light pulses can capture the motion of electrons, just as femtosecond light pulses have captured vibrational motion in molecules.”
To date, the world of attosecond science has primarily been explored by theorists, along with a few seminal experiments. Leone and Neumark are attempting to enhance theoretical insights with practical experiments. But in order to do so, they must design both new instruments and new experiments, and the Keck grant will allow them to do so.
Equipment is currently available to produce 10 femtosecond (10 -14 second) laser pulses. Leone and Neumark will start with this equipment and, using a technique called high harmonic generation, they will manipulate the laser pulses and compress them in time and wavelength to produce pulses of soft x-rays that last about 100 attoseconds (10-16 seconds).
Once the researchers have perfected their equipment, they can begin the experiments to confirm or challenge the findings of the theorists in the attosecond realm. Says Leone, “Most experiments to date have involved studying well-behaved gases. We will extend our techniques to study semi-conductor devices like nanodots and photovoltaic cells.
“It can be difficult to get government funding for high-risk, high-reward research,” noted Leone. “It’s gratifying that the W. M. Keck Foundation is willing to support our research. I think we’ll produce exciting results over the coming years.”
Based in Los Angeles, the W. M. Keck Foundation was established in 1954 by the late W. M. Keck, founder of the Superior Oil Company. The foundation’s grant-making is focused primarily on pioneering efforts in the areas of medical research, science and engineering. The foundation also maintains a program to support undergraduate science and humanities education and a Southern California Grant Program that provides support in the areas of health care, civic and community services, education and the arts, with a special emphasis on children.