{"term":{"id":"04609","title":"photoelectron spectroscopy","longtitle":"IUPAC Gold Book - photoelectron spectroscopy","doi":"10.1351\/goldbook.P04609","code":"P04609","status":"current","also defines":"<em>also defines<\/em>: electron spectroscopy for chemical analysis, UV photoelectron spectroscopy","initialism":"<em>initialism<\/em>: PES","mentioned":"<em>mentioned<\/em>: ESCA, UPS, UV, XPS, Koopmans theorem","definitions":[{"id":1,"text":"A spectroscopic technique which measures the kinetic energy of electrons emitted upon the ionization of a substance by high energy monochromatic photons. A photoelectron spectrum is a plot of the number of electrons emitted versus their kinetic energy. The spectrum consists of bands due to transitions from the ground state of an atom or molecular entity to the ground and excited states of the corresponding radical cation. Approximate interpretations are usually based on 'Koopmans theorem' and yield orbital energies. PES and UPS (UV photoelectron spectroscopy) refer to the spectroscopy using vacuum ultraviolet sources, while ESCA (electron spectroscopy for chemical analysis) and XPS use X-ray sources.","links":[{"term":"ground state","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/G02704"},{"term":"ionization","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/I03183"},{"term":"kinetic energy","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/K03402"},{"term":"radical cation","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/R05073"},{"term":"spectroscopy","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/S05848"},{"term":"ultraviolet","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/UT07492"}],"sources":["Orange Book, 2nd ed., p. 246 (https:\/\/media.iupac.org\/publications\/analytical_compendium\/)","PAC, 1976, 45, 221. 'Nomenclature and Spectral Presentation in Electron Spectroscopy Resulting from Excitation by Photons' on page 223 (https:\/\/doi.org\/10.1351\/pac197645030221)","PAC, 1996, 68, 2223. 'Glossary of terms used in photochemistry (IUPAC Recommendations 1996)' on page 2261 (https:\/\/doi.org\/10.1351\/pac199668122223)"]}],"altoutputs":{"html":"https:\/\/goldbook.iupac.org\/terms\/view\/P04609\/html","xml":"https:\/\/goldbook.iupac.org\/terms\/view\/P04609\/xml","plain":"https:\/\/goldbook.iupac.org\/terms\/view\/P04609\/plain"},"citation":"Citation: 'photoelectron spectroscopy' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351\/goldbook.P04609","license":"The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/) for individual terms.","collection":"If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org .","disclaimer":"The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.","accessed":"2026-04-27T18:04:47+00:00"}}