electron spectroscopy photoelectron spectroscopy photoemission spectrometry Spectroscopy where the sample is illuminated with photons causing ionisation and the emission of photoelectrons, the energies of which are measured. The energy of the incident photons is usually greater than the ionisation energy of the sample and the photoelectrons are emitted with the excess in the form of kinetic energy. PES CHMO:0000387 photoemission spectroscopy PS photoelectron emission spectroscopy photo emission spectrometry photoelectron spectrometry photo emission spectroscopy