L2,3 EDGES OF CHROMIUM - COMPARISON BETWEEN ELECTRON-ENERGY LOSS SPECTRA IN TRANSMISSION AND REFLECTION MODE

The extended fine structure above the Cr L2,3 edges observed in electron energy loss spectra taken both in reflection and in transmission mode has been carefully compared, The good agreement between the structural results obtained by the two measurements confirms the validity of the dipole approximation used to describe the cross section of the electron energy loss spectroscopy in reflection mode. This is particularly surprising because in reflection the primary beam energy is of the same order of the magnitude of the investigated energy loss. This effect is ascribed to the localized spatial extension of the L2,3 wave function. The number of non-dipole terms (monopole transitions) has been shown by a thorough measurement of the L1 ionization edge intensity.