At The Limits Of The Photoelectric Effect
By way of the classical photoeffect, Einstein proved in 1905 that light also has particle characteristics. However, with extremely high light intensities, remarkable things happen in the process. Scientists of the Physikalisch-Technische Bundesanstalt (PTB) have found this out with colleagues at FLASH in Hamburg, the first free-electron laser (FEL) for soft X-rays worldwide. The current models based on Einstein's idea are simply described in such a way: A photon knocks an external electron out of an atom, provided that the photon energy is high enough.
However, with wavelengths of only 13 nanometers and high radiation intensities of several petawatt per square centimeter something else at least with some atoms happens: With xenon, a whole light-wave packet immediately seems to knock out a huge number of internal electrons. This effect is strongly dependent on the material and not only on the characteristics of the exciting radiation, as accepted before. The work, which is currently published in the journal Physical Review Letters, has significance for future experiments of materials research at the new large X-ray laser facilities of the world:
ScienceDaily (Apr. 27, 2009)
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