Relation among x-ray photoelectron intensities,cross sections and kinetic energies in insulating solids

The fundamental relation among X-ray (MgK_α) photoelectron intensities, theoretical orbital ionization cross sections, and photoelectron kinetic energies has been investigated through precisely measured relative intensities of orbital electrons from sublimed-condensed samples of KF, NaF, CaF₂ and KG, and other ionic solids. Although the results confirm within approximately 15% the relation and establish a linear dependence of the intensities on analyzer transmission, they suggest that either a slight deviation from the relation exists or a cancellation of errors occurs. Empirically it is found that the relative intensities are proportional to the square of the ratio of kinetic energies, and with this relation, the intensities agree with the theoretical cross sections within a few per cent. This relation suggests that the dependence on the angular parameter is inconsequential and that the mean free path is proportional to the kinetic energy.