Inner-shell excitations and ionizations of atomic ions by high-energy electron impact

Cross sections for the inner-shell ionization of argon ions by high-energy electron impact are estimated. An improved form of the single-particle model with varying degrees of ionization is used in the calculation of the excitation amplitudes. Partial sums over the allowed final states are carried out using the semiclassical projection operator. This operator depends on a spectral cutoff parameter $e_b$, and a method for its determination is examined for the case of hydrogenic transitions. The ionization cross section incorporates both the direct excitation to the continuum and the Auger emission following the inner-shell excitations. For electron energies in the KeV range and for atomic targets with the core charges $Z_C$ less than 20, the direct ionization dominates, with the excitation Auger-emission mode making a small but appreciable contribution. The ionization cross sections for the neutral neon, and oxygen targets are also estimated.