The energy losses of 60 keV electrons in gadolinium and dysprosium were investigated in order to calculate the energy loss function Im (-1/∊) and the optical constants ∊ 1. ∊ 2 in a large region of energy. The ∊ 2-spectra at lower energies can be explained by band structure calculations. Excitations at higher energies, due to transitions from deeper shells, are found at nearly the same positions as in the case of X-ray absorption.
