Double Electron Ejection in the Photoabsorption Process

Abstract

Electrons ejected from neon by Mg ${K}_{\ensuremath{\alpha}}$ and Al ${K}_{\ensuremath{\alpha}}$ x rays and from argon by Ti ${K}_{\ensuremath{\alpha}}$ x rays have been studied with an electrostatic energy analyzer. On the low-energy side of the photolines characteristic of single electron emission, discrete peaks and continua are observed which respectively indicate excitation and ionization of a second electron. From these electron spectra, the following probabilities of two-electron transitions are derived (per photoabsorption event): Ne $\mathrm{KL}$: (18.5\ifmmode\pm\else\textpm\fi{}1.0)%; Ar $\mathrm{KL}$: (2.5\ifmmode\pm\else\textpm\fi{}0.8)%; and Ar $\mathrm{KM}$: (20.7\ifmmode\pm\else\textpm\fi{}1.4)%. In about 85% of the double events, both electrons go into the continuum; in about 15%, the less tightly bound electron is promoted to excited discrete states. With the use of single-electron Hartree-Fock wave functions, the theory of electron shakeoff accounts for the observed intensities. The shape of the continuum electron spectra is in fair agreement with theoretical predictions. About 80% of the shakeoff electrons have energies of $0\ensuremath{\le}E\ensuremath{\le}{E}_{i}$, where ${E}_{i}$ is the binding energy of the $L$ or $M$ electron in an atom that lacks one $K$ electron. Consequences of the present study in regard to x-ray and Auger-electron satellites are discussed, and it is found that specific satellites can be associated with specific double-hole configurations. The following relative intensities of ${K}_{\ensuremath{\alpha}}$ satellites were measured for Mg, Al, and Ti: 13%, 8.5%, and 4%, respectively.