Attosecond Accuracy

A new technique in studying and measuring the motion in elementary particles, such as electrons is developed in Europe by researchers in physics. The technique consists in measuring how long it takes for electrons to reach the surface of a sample, after being excited by a laser. Photoemission spectroscopy suggests that electrons from the conduction band emerge twice as faster as the bound electrons.

According to Niels Bohr's classical theory of the atom, an electron needs about 150 attoseconds to "orbit" a hydrogen atom, a very fast time compared to the atomic nucleus, pointing at the fact that attosecond spectroscopy can be used to study electron behavior in detail.

The method is simple. An ultraviolet light laser, using a 300-as pulse of ultraviolet light, points towards the sample and ejects electrons through the photoelectric effect. At the same time a long pulse of infrared light is reflected from the solid surface. The electrons ejected through photoelectric effect, are accelerated by the infrared light, towards an electron detector, that times the duration of flight with very high precision. Attosecond spectroscopy of atomic gases has been possible for some time and similar experiments on solids have been limited to about 10 fs resolution.

The new technique developed in Germany was used in studying electrons ejected from a tungsten sample, after absorbing a XUV photon. It was revealed that electrons were ejected from the tungsten sample in two different groups, at a distance of 110 as, and by measuring their kinetic energy they decided that the first group was a burst of conduction electrons, followed by electrons bound in an f-state.

The explanation for the 110 as delay posed no problem for the researchers. About 20 as of this delay is caused by the fact that bound electrons can travel further through tungsten than excited conduction electrons, and the 90 as delay accounts for the expected difference in kinetic energy between the two separate bursts of electrons, that have absorbed the XUV photons shining the solid surface of the sample.

This experiment might open new possible discoveries. Theoretical computations show that an electronic circuit a few atoms across, could switch electric currents at the frequencies of petahetz, almost a million times faster than the current processing power of the fastest processors ever produced.