(chemistry) Any substance that initiates a chemical reaction by the absorption of a photon to form an excited state.

plural of photoinitiator

(chemistry, of a chemical reaction) initiated by light or other electromagnetic radiation

(chemistry, physics) The photoproduction of a radical or ion that is capable of initiating a chain reaction; used especially to initiate polymerization

plural of photoinitiation

present participle of photoinitiate

(chemistry) To initiate a chemical reaction by means of a form of light