Analysis of the photon energy dependent Cu L2,3-M4,5M4,5 Auger-electron spectroscopy spectra of Cu metal and CuO

The variation with photon energy in the Cu L2,3-M4,5M4,5 Auger-electron spectroscopy (AES) (satellite/main line) spectral intensity ratio is analyzed for Cu metal and CuO. It is shown that the variation in the branching ratio of the Auger (or Coster-Kronig (CK)) decay width with the number of the spectator M4,5 hole has to be explicitly taken into account in the analysis. Otherwise, the analysis cannot explain well the variation with photon energy in the AES (satellite/main line) spectral intensity ratio. The branching ratios are determined. They vary fairly significantly with the number of the spectator hole. The L2M4,5-L3M4,5M4,5 CK decay width of CuO becomes almost twice as large as the L2-L3M4,5 one. This is in accord with the variation in the CK decay width with the CK final-state potential. We discussed also why the Cu Lα X-ray emission spectroscopy main line width of CuO is much narrower than the Cu L3 photoelectron spectroscopy main line width.