On the spectral shape of radiation due to Inverse Compton Scattering   close to the maximum cut-off
  The spectral shape of radiation due to Inverse Compton Scattering is analyzed, in the Thomson and the Klein-Nishina regime, for electron distributions with exponential cut-off. We derive analytical, asymptotic expressions for the spectrum close to the maximum cut-off region. We consider monoenergetic, Planckian and Synchrotron photons as target photon fields. These approximations provide a direct link between the distribution of parent electrons and the up-scattered spectrum at the cut-off region. 
E. Lefa, S. R. Kelner, F. A. Aharonian
astro-ph.HE