spectral fluence rate, Eλ,o

Derivative of fluence rate, $E o$ , with respect to wavelength, $λ$ . SI unit is $W m −3$ ; common unit is $W m −2 nm −1$ .

Note:

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.

Source:

PAC, 2007, 79, 293 (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 423