spectral radiant power, \(P_{\lambda}\)

https://doi.org/10.1351/goldbook.S05828
The @R05046@ at @W06659@ \(\lambda \) per unit @W06659@ interval. The SI unit is \(\text{W m}^{-1}\), but a commonly used unit is \(\text{W nm}^{-1}\).
Source:
PAC, 1996, 68, 2223. (Glossary of terms used in photochemistry (IUPAC Recommendations 1996)) on page 2276 [Terms] [Paper]