In a solid, inelastic scattering events also contribute to the photoemission process, generating electron-hole pairs which show up as an inelastic tail on the high BE side of the main photoemission peak. In fact this allows the calculation of electron inelastic mean free path (IMFP). This can be modeled based on the Beer–Lambert law, which states
where  is the IMFP and  is the axis perpendicular to the sample. In fact it is generally the case that the IMFP is only weakly material dependent, but rather strongly dependent on the photoelectron kinetic energy. Quantitatively we can relate  to IMFP by
where  is the mean atomic diameter as calculated by the density so . The above formula was developed by Seah and Dench.