Intensity modulation of the Shirley background of the Cr 3p spectra with photon energies around the Cr 2p edge

The background in X-ray photoelectron spectroscopy data originates, partially, from inelastically scattered photoelectrons. In fact, the current theoretical methods for calculating the background intensity are based on electron energy losses. However, a critical part of the experimental signal, which is known as the Shirley background, cannot be described within the current formalisms. This suggests that the Shirley electrons are not associated with energy losses of photoelectrons and must originate from a different photoexcitation phenomenon with a cross section of its own. We propose a mechanism based on core channeling as the physical origin of the Shirley signal.