As the name suggests, the technique of inverse photoemission spectroscopy (IPES) is the opposite of the much more common X-ray photoemission (XPS) process. It relies on incident low energy electrons interacting with a material’s unoccupied orbitals in the conduction band. As these electrons make the direct transition to fill the unoccupied states the photons that are emitted are measured. These photons are detected as a function of the kinetic energy (KE) of the incident electron beam.
