Oxidation reactions induced by light. Common processes are:

1. Loss of one or more electrons from a chemical species as a result of photoexcitation of that species;
2. Reaction of a substance with oxygen under the influence of ultraviolet, visible, or infrared light. When oxygen remains in the product this latter process is also called photooxygenation. Reactions in which neither the substrate nor the oxygen are electronically excited (i.e., photosensitized oxidations) are sometimes called photoinitiated oxidations.