Hi,
your link does not seem to work properly, it only directs back to this thread. But I might have an idea what your question is leading to.
Generally using wavelength in nm is somewhat impractical if you want to express a Δenergy-value, since the same Δ-wavelength value in nm relates to a different ΔE in dependence if you for example are looking at the same Δnm value at 300 nm or at 800nm. This is why the wavenumber (cm^-1) or eV as Δenergy units are more commonly used in spectroscopy.
Just an example: at 500 nm a Δ50nm difference corresponds to a ΔE of roughly 225 meV or 1818 cm^-1,
at 900 nm however the same Δ50nm difference now correpsonds to a ΔE of roughly 72.5 meV or 585 cm^-1.
Here is a link to a online calculator where you can put in wavelength and wavelength-difference to get the energy value calculated (sorry it is in german, but looking at the units should help :) ):
https://optikexpertisen.de/interaktiv/spektralkonverter
Hope this helps,
Sven