radiant (energy) flux [obsolete], P, Φ

https://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 @P04588@, Φ is reserved for @Q04991@.

Source:
PAC, 2007, 79, 293. 'Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)' on page 409 (https://doi.org/10.1351/pac200779030293)