Norrish Type II photoreaction 

https://doi.org/10.1351/goldbook.N04218
Intramolecular abstraction of a γ-hydrogen by an excited carbonyl compound to produce a 1,4-diradical as a primary photoproduct.
Note:
An example is:
Source:
PAC, 2007, 79, 293. (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 375 [Terms] [Paper]
Citation: 'Norrish Type II photoreaction' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.N04218 RIS BibTex EndNote
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Last revised: February 24, 2014