02389 IUPAC Gold Book - fine structure constant 10.1351/goldbook.F02389 F02389 current constant 1 Atomic fundamental physical constant, \(\alpha =\frac{\mu _{0}\ e^{2}\ c_{0}}{2\ h} = 7.297\ 353\ 08\ \left(33\right)\times 10^{-3}\), where \(\mu _{0}\) is the permeability of vacuum, \(e\) the elementary charge, \(h\) the Planck constant, and \(c_{0}\) the speed of light. Planck constant https://goldbook.iupac.org//terms/view/P04685 elementary charge https://goldbook.iupac.org//terms/view/E02032 permeability of vacuum https://goldbook.iupac.org//terms/view/P04504 CODATA Bull. 1986, 63, 1 (https://doi.org/10.6028/jres.092.010) https://goldbook.iupac.org/terms/view/F02389/html https://goldbook.iupac.org/terms/view/F02389/json https://goldbook.iupac.org/terms/view/F02389/plain Citation: 'fine structure constant' 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.F02389 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. 2026-04-20T13:13:53+00:00