Satellite structure in the x-ray photoelectron spectra of rare gases and alkali-metal halides

The photoelectron spectra as the result of photoionization in the various subshells of Ar, Kr, and Xe have been studied using $\mathrm{Al}K\alpha$ (1487 eV), $\mathrm{Mg}K\alpha$ (1254 eV), and in some cases $\mathrm{Zr}{M}_{\zeta }$ (151 eV) x rays. In addition to the main photoelectron peaks there appears satellite structure at slightly lower kinetic energy. When photoionization occurs in the core levels, this structure can be explained as an electron shakeup in terms of the sudden approximation, and the experimental results are compared with Hartree-Fock calculations of the expected excited states. When photoionization occurs in the valence shell, two-electron excitations leading to the configuration-interaction states $n{s}^{2}n{p}^{4}n{d}^1{}_{}{}^2{}_{}{}^{}S$ are found to be the dominant processes. Photoelectron spectra were also taken of the valence shell of solid alkali-metal halides, and the satellite structure compared with that of the rare gases. From our results similar phenomena seem to occur with the alkali-metal ions, although the intensities are greater than in the case of the rare gases.