Title: multiplicity
Long Title: IUPAC Gold Book - multiplicity
DOI: 10.1351/goldbook.M04062
Status: current

Definition
The number of possible orientations, calculated as \(2\ S+1\), of the spin angular momentum corresponding to a given total spin quantum number (\(S\)), for the same spatial electronic wavefunction. A state of singlet multiplicity has \(S=0\) and \(2\ S+1=1\). A doublet state has \(S=\frac{1}{2}\), \(2\ S+1=2\), etc. Note that when \(S>L\) (the total orbital angular momentum possible) there are only \(2\ L+1\) orientations of total angular momentum possible.

Related Terms
- angular momentum: https://goldbook.iupac.org//terms/view/A00353
- doublet state: https://goldbook.iupac.org//terms/view/D01853

Source
- PAC, 1996, 68, 2223. 'Glossary of terms used in photochemistry (IUPAC Recommendations 1996)' on page 2255 (https://doi.org/10.1351/pac199668122223)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/M04062/html
- json: https://goldbook.iupac.org/terms/view/M04062/json
- xml: https://goldbook.iupac.org/terms/view/M04062/xml

Citation: Citation: 'multiplicity' 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.M04062
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Accessed: 2026-06-20T19:05:55+00:00