The electronic structure of materials not only is fascinating from a theoretical point of view, but also has tremendous implications for technology. Electronic‐structure studies, in fact, account for the majority of uses of uv radiation from synchrotron sources. Most of these studies involve photoelectron spectroscopy, a measurement technique that goes to the heart of many problems in atomic, molecular and condensed‐matter physics. For example, photoelectron spectroscopy permits direct measurement of all quantum numbers of the electronic states in a material, and in particular determination of its band structure—that is, the relationship between energy and momentum of electrons in the material.
With its power enhanced by synchrotron radiation, this technique for studying bulk and surface electronic structures goes to the heart of many problems in atomic, molecular and condensed‐matter physics.