09306 IUPAC Gold Book - asymmetry parameter 10.1351/goldbook.09306 09306 current 1 In X-ray photoelectron spectroscopy factor which characterizes the intensity distribution, \(L(\gamma)\), of photoelectrons ejected by X-rays from isolated atoms at an angle \(\gamma\) from the incident X-ray direction. In the dipole approximation, \(L(\gamma) = 1 + ½\beta [3(\sin^{2}\gamma)/2-1]\). This formula relates to gases and is modified by the effects of elastic scattering when applied to solids. At the magic angle, \(L(\gamma) = 1\). PAC, 2020, 92, 1781. 'Glossary of methods and terms used in surface chemical analysis (IUPAC Recommendations 2020)' on page 1820 (https://doi.org/10.1515/pac-2019-0404) https://goldbook.iupac.org/terms/view/09306/html https://goldbook.iupac.org/terms/view/09306/json https://goldbook.iupac.org/terms/view/09306/plain Citation: 'asymmetry parameter' 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.09306 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. If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org . 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. 2026-06-28T12:58:25+00:00