Resonance excitation of the 3p6-subshell in potassium: Contribution to the single ionization

The total autoionization cross-section of potassium has been studied as a function of incident electron energy over the range from the lowest autoionization threshold at 18.72 eV to 24.4 eV and at an energy resolution of 0.25 eV. The cross-section has been obtained by determining the normalized total intensities of ejected-electron spectra accurately measured at the magic angle of 54.7°. The structure observed in the autoionization function has been assigned to the negative-ion resonances based upon the lowest autoionizing configurations 3p54s2 and 3p53d4s. The quartet levels from the 3p53d4s configuration give the bulk of the autoionization contribution in the single ionization cross-section in the energy range 20.5-24.4 eV. Comparison of the present results with earlier available experimental and theoretical results is presented.