New developments are producing to ever more accurate time technologies

Researchers used short pulses of laser light to produce images of electrons leaving atoms and recorded what happened to within 100 attoseconds.

To imagine how long this is, if 100 attoseconds is stretched so that it lasts one second, one second would last 300 million years on the same scale.

Scientists used the technique to record the dynamics of electrons in atoms and report their findings in Nature.

The research team employed extreme ultraviolet (XUV) light pulses to excite atoms, prompting them to emit electrons, the small negatively charged particles that are a fundamental part of every atom.

"We accelerate the electrons spinning around the nucleus. Some pick up so much energy that they leave the atoms forever," Professor Ferenc Krausz, of the Technische Universitat Wien, in Austria, told BBC News Online.

Future clocks

At the same time, the scientists used a device called a Few-Cycle Laser to capture "tomographic images" of these electrons that gave information about how they behaved with time.

This allowed the scientists to distinguish events within 100 attoseconds, the shortest interval of time ever recorded.

THE ATTOSECOND An attosecond is one quintillionth (10 to the power of minus 18) of a second Caesium atomic clocks are accurate to one second over many millions of years The development of laser counters will push clocks to theoretical billion-year accuracy The clocks' technology will be used in telecommunications and experiments testing fundamental theories in physics They will also be used to time important processes in biologocal cells, to aid our understanding of disease

Existing atomic clocks are very accurate and measure time by counting the number of times caesium atoms jump back and forth between different energy levels.

These jumps, or "ticks", occur at microwave frequencies. But researchers are increasingly looking to count ticks using optical frequencies, with the help of lasers.

This would offer the prospect of more stable and therefore more accurate clocks.

"The more stable the clock, the better you can measure time," said Dale Henderson of the UK's National Physical Laboratory.