On analyzing the intrinsic processes through the Shirley background correction procedure

The process of creating photoelectrons in solids is strongly connected to different kinds of energy loss processes, classified as 'extrinsic' and 'intrinsic'. In measured spectra the peaks are sensitively affected by all these processes. Of course one tries to extract from the spectrum shape as much information on these processes as possible. Unfortunately, the different loss processes are inextricably mixed. In theoretical works it is of course possible to consider these contributions separately, so some authors try to derive these contributions from the experimental spectra, too. The task is hard and the methods used for this goal are not always appropriate. Some popular methods are clearly based on misunderstanding or misusing the popular Shirley background correction method. This work explores the origin of some such problems and explains why those results (like density of states, intrinsic background, inelastic shape, etc.) based on inappropriately used methods are unreliable.