The Shirley background revised

Some aspects of the theory and the practical application of the Shirley background correction procedure are reviewed. The 'classic' Shirley/Sherwood method is scrutinized, with special emphasis on the physical meaning and the correct implementation. The features of the classic and the cross-section-based Shirley background correction procedures are compared. With a simple modification to the recently discovered Shirley-equivalent inelastic energy loss cross-section a 'physical' cross-section is derived and its impact on the practical data evaluation is analyzed. The impact of some frequently used erroneous implementations on the physical meaning of the evaluation procedure as well as the practical results derived using the wrong implementation are discussed and the correct statement on the physical meaning and implementation method is also suggested.