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When Speeding Bullets Seem Slow

Science at SLAC is changing. It's an evolution driven by new tools and techniques—advances in laser science are enabling researchers to peer deeper than ever before into the world of ultrafast phenomena. In the August 9 edition of the journal Science, SLAC's director of Photon Ultrafast Laser Science and Engineering (PULSE) Center, Philip Bucksbaum, describes the future of this new, ultrafast or "attosecond" science.

An attosecond may seem like an impossibly brief sliver of time—one attosecond is as short, compared to a full second, as one second is short compared to the age of the entire universe (about 14 billion years, or 400 quadrillion seconds). But within a few tens or hundreds of attoseconds, many processes occur that are fundamental to the world we live in. Metals, for example, are reflective because of the attosecond response of their electrons to light. Electrons also rearrange within atoms in a few attoseconds, motions that ultimately form the basis of all chemistry.

Attosecond processes have been studied indirectly for years in particle decays, using the Heisenberg Uncertainty Principle, which states that very rapid changes must have a correspondingly large spread, or "uncertainty," in their energy. Now, thanks to advancements in tools and techniques, according to Bucksbaum, these ultrafast phenomena may be be studied directly. SLAC's PULSE Center is leading the charge in this rapidly evolving field, with three laser labs at SLAC and two on Stanford's main campus dedicated to pioneering new techniques for understanding ultrafast dynamics. The Linac Coherent Light Source, scheduled to begin operation in 2010, will serve as an ideal platform for advancing the field even further by creating ultrafast pulses of hard x-rays used to probe the dynamics of matter on the atomic scale.

On-site users can download Bucksbaum's paper from the Science Magazine website.

—Brad Plummer, SLAC Today, August 31, 2007

Above image: (Top left) A mathematical depiction of the outermost electron in a carbon dioxide atom. Additional frames show a simulation of what happens to the atom, over the course of 120 attoseconds, when an electron is ejected by a strong laser pulse and then recollides with its parent ion.