Photoemission (sometimes also called Photoemission Spectroscopy or PES) is a spectroscopy technique very useful for studies of the electronic structure of solid materials. It is especially useful for studies of ordered (crystalline) materials: elemental metals and semiconductors as well as inorganic and organic compounds. The principle is illustrated on a diagram below. A photon beam from a well-characterized source (arc lamp, laser or synchrotron radiation) is directed at the sample surface. These photons depending on their energy can excite electrons in the solid and some of these excited electrons will escape from the solid. Analyzing the energy and direction (momentum) of the emitted electrons one can gather information about the electronic states of the studied material.

Two very important components for this technique are the light source and the electron analyzer. Arc lamps and lasers are used as light sources in the laboratories but for materials studies it is very convenient to use Synchrotron Radiation as a light source, because it produces very intense beams of polarized in the suitable energy range (10 - few 100's eV).
On the electron analyzer side there has been a lot of progress recently with developing detectors capable of simultaneously analyzing the energy and angular distribution of electrons emitted within 10-15⁰ angular range. An example of such an analyzer called Scienta is shown below. More details on using this type of an analyzer at the synchrotron can be found on the SRC website.

Large GIF image (~62 KB) with an example of PES data for Cu acquired with Scienta.

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