Comparison between optically excited and electron-excited transitions above oxygen and nitrogen K edges in Cu2O, O/Al, O/Ni, SiO2 and Si3N4

We compare transitions observed in photoabsorption spectra above the oxygen and nitrogen K edges in several compounds and chemisorption systems with transitions excited by the process of electron-energy loss detected in the reflection mode. We find few but significant discrepancies between the two, mainly attributable to quadrupole transitions and double inelastic scattering in the electron-energy-loss spectra. The problem of the extraction of structural information from the measurements is considered.