Double Electron Ejection in the Photoabsorption Process

Electrons ejected from neon by Mg $K_{\alpha }$ and Al $K_{\alpha }$ x rays and from argon by Ti $K_{\alpha }$ 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±1.0)%; Ar $\mathrm{KL}$: (2.5±0.8)%; and Ar $\mathrm{KM}$: (20.7±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 $0\le E\le E_i$, 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 $K_{\alpha }$ satellites were measured for Mg, Al, and Ti: 13%, 8.5%, and 4%, respectively.