Excitation energy dependence of the photoemission spectra of metals

The x-ray photoemission spectra (XPS) of simple metals are investigated by using the methods of many-body perturbation theory. Several features of the XPS, such as the infrared catastrophe effect, the effect of intrinsic and extrinsic plasmon production, etc., have previously been considered in different approximations by various authors. In this paper, a unified theory, using a nonseparable core-hole conduction-electron scattering potential, is proposed to describe these features with special attention to the interference effects. The evolution of the shapes of the main line and the first plasmon satellite along with the background is considered as a function of the incident x-ray energy. Numerical results of the intensity and the shape of these lines are presented for Na and A1 for the incident photon energies of $5{\omega }_p$ and $90{\omega }_p$.