Electron Double Ionization Cross Section in Sodium Obtained from Kα^h Hypersatellite Spectra

The Kα^h hypersatellite spectrum of Na metal has been measured in electron excitation with voltages from 4 to 25 kV. The spectrum shows lines with initial K ^-2 (Kα₂^h) and K ^-2 L ^-1 holes. The energies of these lines as well as the K ² binding energy have been determined and compared with theoretical calculations. The intensity of the line group with K ^-2 L ^-1 initial configuration relative to the K ^-2 group has been measured and found to be in agreement with simple shake-off calculation. The electron double ionization cross section (EDC) of the K-shell has been determined from both thick and thin target measurements using the method developed by Saijonmaa and Keski-Rahkonen, and found to yield equivalent results. The EDC has also been calculated theoretically using classical and quantum mechanical binary encounter approximations as devised by Saijonmaa. Theory reproduces fairly well the magnitude and the atomic number dependence of the EDC whereas the shape of the EDC-curve as function of energy deviates clearly from observed values.