spectral fluence rate, E λ , o

Derivative of fluence rate, E o, with respect to wavelength, λ. SI unit is W m −3; common unit is W m −2 nm −1.
All spectral terms may also be defined as derivatives with respect to frequency, ν, or wavenumber, ν ˜, and are referred to, when necessary, as in terms of wavelength, or frequency or wavenumber, respectively.
PAC, 2007, 79, 293 (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 423