IPES probes the empty density of states above the Fermi level of conduction/valence band in condensed matter. Energy of the impinging electron is varied while photons are detected at fixed energy, obtaining the spectrum of the density of unoccupied states. Combined with PES, it gives information on the surface electronic transport gap of sample.

Valence photoemission in resonance with core photo-ionization allows to study charge transfers between adsorbate species and the substrate surface and their time scale. If polarisation and emission angles are considered, specific atomic sites/bonds are probed. The technique is useful when electron-hole creation and transport phenomena are involved.

XPS is a surface spectroscopic technique for quantitative measurements of the elemental composition or stoichiometry and the chemical state of the present elements, like their oxidation state and chemical bonds. XPS is highly surface sensitive, giving chemical and binding energy information from the a narrow region close to the surface.

ARPES allows to measure directly the electronic band structure of crystalline solids. Electrons are detected retrieving information about initial state energy, momentum and spin.

Ultraviolet photoelectron spectroscopy (UPS), also described as photoemission spectroscopy (PES) when applied to measurements on solid surfaces, is a technique suitable for measuring the spectral features that are close to the Fermi level for surfaces or adsorbates. UPS is particularly useful for determining the work function of a material.