spectral radiant energy, Q λ

https://dx.doi.org/10.1351/goldbook.ST07480
Derivative of radiant energy, Q, with respect to wavelengthλ. SI unit is J m −1; common unit is J nm −1.
Source:
PAC, 2007, 79, 293 (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 425