Magneto-optics as a tool to study occupied and empty 4f and 5f states

Magneto-optical spectroscopy is known to be particularly powerful for studying occupied 4f and 5f states through f→d excitations. The recent discovery of d→f transitions in LaSe has revived the idea to use magneto-optical spectroscopy also to study empty f states. We review the state of the art of optical and magneto-optical investigations of occupied and empty f states for lanthanum, cerium and uranium monochalcogenides and monopnictides. (orig.)