Practical guide for inelastic mean free paths, effective attenuation lengths, mean escape depths, and information depths in x-ray photoelectron spectroscopy

Information is provided on four terms that are used for different purposes in x-ray photoelectron spectroscopy (XPS): the inelastic mean free path (IMFP), the effective attenuation length (EAL), the mean escape depth (MED), and the information depth (ID). While the IMFP is a parameter that depends on both the material and electron energy, the other three terms depend on the IMFP, the instrumental configuration, and the magnitude of elastic-scattering effects in the sample material. In addition, different EALs can be defined for different XPS applications, and the numerical values for each application can differ. Guidance is given on sources of IMFP and EAL data and on predictive equations for IMFPs, EALs, MEDs, and IDs. This guide is one of a series intended to highlight best practices in the use of XPS.