K-SHELL IONIZATION OF ATOMS BY ELECTRON-IMPACT

K-shell ionization cross sections of silver and gold due to electron i mpact, with electron energies varying from the ionization threshold to 1 GeV, are calculated. Within the framework of the plane wave Born ap proximation, with corrections for exchange, Coulomb and relativistic e ffects, longitudinal as well as transverse interactions of the virtual photons with the atoms are taken into account. Good agreement between the theory and the experiments has been obtained over the whole energ y range. Simple analytical expressions, valid for all atoms with Z gre ater than or equal to 6, for the K-shell Bethe parameters in terms of a single atomic property are also given.