Atomic‐level characterization of materials with core‐ and valence‐level photoemission: basic phenomena and future directions

In this overview, the basic concepts of core and valence photoelectron spectroscopy (photoemission), photoelectron diffraction, and photoelectron holography are introduced. Then some current developments in these techniques that should enhance their utility for atomic‐level characterization of new materials and surface chemical processes are discussed, including measurements with hard X‐ray excitation, standing‐wave excitation, and ambient pressures in the multi‐torr regime.