I am interested in using the interstellar radiation field data from astro-ph/0507119. I have downloaded the fits file from the galprop page. The fits header says that they are microns eV cm^-3 microns^-1. Am I correct in assuming that the data is therefore 1/ \lambda *dU/d\lambda, where U(E) is the energy density in eV/cm^3? Or is it rather 1/lambda dU/d(1/lambda)? It's a crucial distinction.

thanks for your time.

Aaron