entrainment

in photochemistry
https://doi.org/10.1351/goldbook.ET07371
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.
Note:
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.
Source:
PAC, 2007, 79, 293. 'Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)' on page 335 (https://doi.org/10.1351/pac200779030293)