Photoelectron spectroscopy involves the measurement of kinetic energy of photoelectrons to determine the bonding energy,intensity and angular distributions of these electrons and use the information obtained to examine the electronic structure of molecules. Applications of Photoelectron Spectroscopy Photoelectron spectroscopy (PES) is a technique used for determining the ionization potentials of molecules. Underneath the banner of PES are two separate techniques for quantitative and qualitative measurements. They are ultraviolet photoeclectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS). XPS is also known under its former name of electron spectroscopy for chemical analysis (ESCA). UPS focuses on inoization of valence electrons, while XPS involves ionizing core electrons. Photoelectron Spectroscopy Photoelectron spectroscopy involves the measurement of kinetic energy of photoelectrons to determine the binding energy, intensity and angular distributions of these electrons and use the information obtained to examine the electronic structure of molecules. It differs from the conventional methods of spectroscopy in that it detects electrons rather than photons to study electronic structures of a material. Thumbnail: Photoelectric effect underlies photoelectron spectroscopy. (CC BY-NC; Laura Guerin via CK-12 Foundation)