The cleavage of one or more covalent bonds in a molecular entity resulting from absorption of light, or a photochemical process in which such cleavage is an essential part. For example:
The term is used incorrectly to describe irradiation of a sample, although in the combination flash photolysis this usage is accepted.
PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1150 (https://doi.org/10.1351/pac199466051077)