Title: intersystem crossing
Long Title: IUPAC Gold Book - intersystem crossing
DOI: 10.1351/goldbook.I03123
Status: current

Definition
A photophysical process. An isoenergetic radiationless transition between two electronic states having different multiplicities. It often results in a vibrationally excited molecular entity in the lower electronic state, which then usually deactivates to its lowest vibrational level.

Related Terms
- avoided crossing: https://goldbook.iupac.org//terms/view/A00544
- electronic state: https://goldbook.iupac.org//terms/view/ET07026
- radiationless transition: https://goldbook.iupac.org//terms/view/R05057
- surface crossing: https://goldbook.iupac.org//terms/view/S06166

Source
- PAC, 1996, 68, 2223. 'Glossary of terms used in photochemistry (IUPAC Recommendations 1996)' on page 2248 (https://doi.org/10.1351/pac199668122223)

Related Reference
- Orange Book, 2nd ed., p. 187 (https://media.iupac.org/publications/analytical_compendium/)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/I03123/html
- json: https://goldbook.iupac.org/terms/view/I03123/json
- xml: https://goldbook.iupac.org/terms/view/I03123/xml

Citation: Citation: 'intersystem crossing' 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.I03123
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Accessed: 2026-05-18T10:23:05+00:00