Electron slowing-down flux spectrum inAl2O3

An electron slowing-down flux spectrum has been measured for $\beta$ particles, $\delta$ rays, and secondaries generated by the $\beta$ decay of neutron-activated ${}_{}{}^{164}{}_{}{}^{}\mathrm{Dy}$ uniformly distributed in ${\mathrm{Al}}_2$ ${\mathrm{O}}_3$. The energy range covered in these measurements extends from 1.5 eV to 32 keV. Fairly good agreement with predictions of the Spencer-Fano theory is found for energies above 10 keV. The overall shape of the spectrum is similar to that found earlier for metals and semiconductors. A companion theoretical calculation has been carried out based on cross sections for ionization of electrons from the inner shells of Al and O derived from generalized oscillator strengths, and on cross sections for valence-band electrons derived from a model-insulator theory. The effect of Auger cascade electrons is also included in the numerical solution of the electron slowing-down cascade equation. The theoretical spectra are smaller than the experimental results by as much as a factor of 4 in the energy range from 50 to 2000 eV.