alkene photodimerization

Photochemical process leading to the formation of a cyclobutane from two identical alkenes, i.e., from the photocycloaddition of an electronically excited alkene to a ground-state alkene.
Source:
PAC, 2007, 79, 293 (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 301