Title: fine structure constant
Long Title: IUPAC Gold Book - fine structure constant
DOI: 10.1351/goldbook.F02389
Status: current
Index: constant

Definition
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.

Related Terms
- 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

Source
- CODATA Bull. 1986, 63, 1 (https://doi.org/10.6028/jres.092.010)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/F02389/html
- json: https://goldbook.iupac.org/terms/view/F02389/json
- xml: https://goldbook.iupac.org/terms/view/F02389/xml

Citation: 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
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Accessed: 2026-04-20T13:13:46+00:00