The surge of growth in surface science, demonstrated by this special issue of PHYSICS TODAY, can be attributed to several complementary factors. First, the gas–solid interface is amenable to investigation by many new research tools that involve various combinations of electrons, photons, ions, electric fields and so on. Second, the insights and information obtained from modern surface‐science experiments are useful to many technologically important fields, such as catalysis,corrosion and semiconductor devices among others. Third, two‐dimensional interfaces such as the gas–solid interface constitute a distinct phase of condensed matter with unique properties that we are only beginning to understand—thus, studies of solid surfaces are an attractive “new frontier” for materials scientists and are being vigorously explored.
Studies of intrinsic surface states and of absorbate surface states, both at ultraviolet and x‐ray photon energies, are among the many applications of this versatile probe.