Excitation-autoionization of the 5p6 subshell in Ba atoms

Abstract

The excitation-autoionization cross section for the 5p6 subshell in Ba atoms was determined in an incident electron energy range from the lowest autoionization threshold at 15.61 eV up to 600 eV. The data were obtained by measuring the total intensity of ejected-electron spectra arising from the decay of the 5p5n1l1n2l2n3l3 autoionizing states. The energy behavior of the cross section is characterized by the presence of a strong resonance structure in the near-threshold energy region of 15.6–22.7 eV as well as a broad maximum around 80 eV. The cross section reaches its maximum value of (3.2 ± 1.0)×10−16 cm2 at 17.4 eV, which makes out a contribution of up to 25% to the total single-ionization cross section of Ba atoms. The role of particular configurations in formation of the cross section is considered on the basis of the spectroscopic classification and excitation dynamics of the 5p5n1l1n2l2n3l3 autoionizing states.