spectral radiant intensity, \(I_{\lambda}\)

https://doi.org/10.1351/goldbook.S05827
The radiation intensity, \(I\) at @[email protected] \(\lambda \) per unit @[email protected] interval. The SI unit is \(\text{W m}^{-1}\ \text{sr}^{-1}\), but a commonly used unit is \(\text{W nm}^{-1}\ \text{sr}^{-1}\).
Source:
PAC, 1996, 68, 2223. (Glossary of terms used in photochemistry (IUPAC Recommendations 1996)) on page 2276 [Terms] [Paper]