primary (photo)product

https://doi.org/10.1351/goldbook.P04840
The first observable chemical entity which is produced in the primary photochemical process and which is chemically different from the reactant.
See:
primary (photo)process
Source:
PAC, 1996, 68, 2223. (Glossary of terms used in photochemistry (IUPAC Recommendations 1996)) on page 2266 [Terms] [Paper]