Cross section ratios of double-to-single K-shell ionization induced by electron impact in metallic Sc, Cr and Cu targets

The double K-shell ionization of Sc, Cr and Cu induced by electron impact was investigated via high energy resolution measurements of the K alpha diagram transitions and the transitions resulting from the radiative decay of K-shell double vacancy states, namely the K-h alpha hypersatellites. For Sc, the K beta diagram lines and K-h beta hypersatellites were also measured. The measurements were carried out in-house with a von Hamos curved crystal spectrometer operated in the so-called direct geometry in which the anodes of Sc, Cr and Cu X-ray tubes were used as targets. For each element, the electron kinetic energy was chosen to be about twice the threshold energy for the double 1s ionization. The double-to-single ionization cross-sections ratios P-KK were deduced from the hypersatellite-to-diagram line yield ratios, corrected beforehand for the self-absorption of the X-rays in the target and the energy dependent efficiency of the spectrometer. The obtained ratios are discussed and compared to other P-KK values found in the literature for electrons and photons.