Reduction reactions induced by light. Common processes are: 1, addition of one or
more electrons to a photoexcited species; 2, the photochemical hydrogenation of a
substance. Reactions in which the substrate is not electronically excited are sometimes
called photoinitiated reductions.
Source:
PAC, 1996, 68, 2223
(Glossary of terms used in photochemistry (IUPAC Recommendations 1996))
on page 2264