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(Static) photoemission

(Static) photoemission

The photoemission technique is based on the photoelectric effect, explained by Albert Einstein in 1905, who was awarded the Nobel prize in 1921 because of its explanation. This phenomenon consists of the extraction of electrons in an illuminated material when the radiation is energetic enough. If both the kinetic energy and the emission angle of the emitted electron are detected, it is possible to determine de initial state at the material. Angle resolved photoemission (ARPES) allows therefore to determine the band structure of the studied system or the chemical composition by analysis of the core levels in the material.

Radiation sources to illuminate the sample can either be ultraviolet lamps, lasers, cathode-ray tubes or even synchrotrons like SOLEIL. In the synchrotrons, charged particles are stored in rings to use their wide spectra of emitted wavelengths.

Principle of angle-resolved photoemission. When photons illuminate a sample, electrons are emitted by photoelectric effect. The energy and momentum conservation at the surface allow to determine the initial state of the electron in the solid.

Film on photoemission principle. Courtesy of Julien Bobroff.