As the name suggests, the technique of inverse photoemission spectroscopy (IPES) is the opposite of the much more common photoemission (XPS) process.  It relies on incident low energy electrons interating with a materials 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.

The AXIS Supra⁺ spectrometer can be configured with IPES on the sample analysis chamber or surface science station.