Interference of O Kα ghost features in X-ray-excited Auger spectra

We have noted the interference of O Kα ghost peaks in spectra obtained using unmonochromatized X-ray sources, particularly in C(KVV) and O(KVV) X-ray-excited Auger spectra. The source of the undesirable O Kα photons is a surface oxide on the Mg or Al anode of the polychromatic X-ray sources used. A calculation of the oxide thickness required to give the observed ghost intensity in measurements on a gold sample using a heavily oxidized Mg anode is given and the estimated oxide thickness found plausible. Since it may be impossible to operate the anode with no oxide present, the use of standard Au sample is suggested as an excellent test for the presence of O Kα X-radiation from unmonochromatized X-ray sources. (orig.)