 Inverse photoemission spectroscopy

Inverse photoemission spectroscopy injects an electron of known kinetic energy into a sample and detects the photon emitted as it enters an unoccupied electronic state. Conservation of energy, together with incident-angle information and an appropriate surface model, probes the unoccupied electronic band structure. Ordinary angle-resolved photoemission spectroscopy instead removes electrons from occupied states.

Inverse photoemission spectroscopy (IPES) is a powerful experimental technique used to study the electronic states of materials, particularly surfaces and interfaces. In contrast to traditional photoemission spectroscopy (PES), which involves the excitation of electrons from a material by incident photons (measuring the emitted electrons), IPES involves the injection of electrons into a material, where these electrons can excite the material and subsequently emit photons.