X-ray photoelectron spectroscopy abbr., XPSР; ESCA (rus. спектроскопия, рентгеновская фотоэлектронная otherwise электронная спектроскопия для химического анализа abbr., ФЭС; ЭСХА) — a type of photoelectron spectroscopy where photoelectrons are excited by X-rays and which serves to probe deep (core) electron levels.


Laboratory sources for XPS are X-ray tubes where X-rays are generated by bombarding a target with high-energy electrons. The most usual target materials are Mg and Al which ensure radiation with a photon energy of 1253.6 eV and 1486.6 eV, respectively. Since photoemission probability is maximum at a photon energy close to the ionisation threshold and drops down rapidly when the photon energy greatly exceeds the electron-binding energy, XPS is a method to study deep core levels. In XPS spectra core levels show themselves as sharp peaks. The energy position of the peaks gives information on what chemical elements are present in the sample as well as on their chemical environment which is manifested in the so-called chemical shifts, changes in the peaks' position by a value of from 1 to 10 eV when chemical bonds are being formed. A peak's intensity gives information about the concentration of a given element in the sample, for which reason XPS is most often used to analyse the chemical composition of samples.

An alternative name of this method, electron spectroscopy for chemical analysis (ESCA), was introduced by the founder of this method (K.M. Siegbahn) who received the Nobel Prize in Physics in 1981 "for contributions to the development of high-resolution electron spectroscopy". Today, the term ESCA is not widely used.


  • Zotov Andrey V.
  • Saranin Alexander A.


  1. Oura K. et al. Surface Science: An Introduction // Springer, 2010 - 452 pp.

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