radiant (energy) flux, P,Φ [obsolete]

https://dx.doi.org/10.1351/goldbook.R05044
This obsolete term is not recommended. In photochemistry, radiant power, P, is adopted. SI unit is W.
Note:
P is preferred, because in photochemistry, Φ is reserved for quantum yield.
Source:
PAC, 2007, 79, 293 (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 409