Term used in photostimulated radical nucleophilic substitution to designate the induction of the reaction of a less reactive (or non-reactive) nucleophile with a substrate by the addition of catalytic amounts of another nucleophile, more reactive at initiation. Often, the non-reactive nucleophile at initiation is, however, quite reactive at propagation.
Term also used in @PT07445@ in connection with the setting of the circadian clock by biological photosensors such as phytochromes and cryptochromes in plants and cryptochromes in mammals and insects.
PAC, 2007, 79, 293. 'Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)' on page 335 (https://doi.org/10.1351/pac200779030293)