Title: σ → σ* transition
Long Title: IUPAC Gold Book - σ → σ* transition
DOI: 10.1351/goldbook.S05435
Status: current

Definition
An electronic transition described approximately as promotion of an electron from a 'bonding' $\ce{\upsigma\!\mbox{-}orbital}$ to an 'antibonding' $\ce{\upsigma\!\mbox{-}orbital}$ designated as \(\sigma ^{\rm{*}}\). Such transitions generally involve high transition energies, and appear close to or mixed with Rydberg transitions.

Related Terms
- Rydberg transitions: https://goldbook.iupac.org/terms/view/R05432
- promotion: https://goldbook.iupac.org/terms/view/P04877

Source
- PAC, 1996, 68, 2223. 'Glossary of terms used in photochemistry (IUPAC Recommendations 1996)' on page 2279 (https://doi.org/10.1351/pac199668122223)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/S05435/html
- json: https://goldbook.iupac.org/terms/view/S05435/json
- xml: https://goldbook.iupac.org/terms/view/S05435/xml

Citation: Citation: 'σ → σ* transition' 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.S05435
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Accessed: 2026-06-28T17:17:02+00:00