ULTRAFAST lasers which help to make some of the shortest pulses of light seen in the UK, will be at the heart of a new system to capture the movements of electrons as they whizz around the nucleus of atoms.

Existing apparatus at Imperial for high harmonic generation, a process that will be harnessed for attosecond pulse production

A £3.5 million research grant from the UK Research Councils' Basic Technology Programme, will help Imperial scientists and others to develop and build the first attosecond laser system capable of

freeze-framing and controlling the motion of electrons.

Researchers hope that the system will reveal fundamental insights into atomic behaviour and may eventually lead to new applications in molecular and surface sciences, nano-scale and biological structures.

Electrons move extremely quickly - their motion is measured in units of time called attoseconds. One attosecond is one billion-billionth of a second, and an electron orbits a hydrogen atom in just 24 attoseconds, or 24 billion-billionths of a second.

To capture the electron in motion, researchers will build a system to produce pulses of light lasting attoseconds. These pulses will then be strobed on to atoms in order to 'freeze' their electrons in motion.

"If you want to see a bullet ripping through a tomato you need to have a microsecond strobe to freeze the motion of the projectile," said Dr John Tisch, project manager, department of physics. "We want to see electron motion and for that we need attosecond resolution. Without attosecond probes, the electron motion would be just a 'blur.' "

Electrons, behind all fundamental processes in chemistry, biology and material sciences, make the 'bonds' in matter, joining atoms together to form larger systems like molecules.

The planned length of the pulses in the UK attosecond system, generated using a technique known as high harmonic generation, will be about 200 attoseconds.

"Changes in materials - whether molecules, solids or living tissue - can all be traced back to rearrangement of these bonding electrons," added Professor Jon Marangos, project coordinator. "Attosecond pulses will give us the ability, for the first time, to measure and probe these very fast changes and shed new light on the dynamic processes that occur on this unexplored timescale."

More than 30 scientists are expected to contribute to the four year project. The groups, also comprising researchers from Kings College London, and the universities of Oxford, Reading, Birmingham, Newcastle and the Rutherford Appleton Laboratory, Oxfordshire, will each build separate components.

The final working system will be assembled and operated at Imperial College by 2005.