Electron impact excitation of the (3p⁵4s²)²P_3/2,1/2autoionizing states in potassium

Ejected-electron excitation functions for the lowest-lying (3p54s2)2P3/2 and (3p54s2)2P1/2 autoionizing states in potassium have been measured for incident-electron energies from threshold to 500 eV and 200 eV, respectively, with improved energy resolution. Strong resonances have been observed and well resolved in the excitation functions of both states near their excitation thresholds. R-matrix (close-coupling) calculations were performed to analyse and tentatively assign these features. A remarkable similarity between the spectrum of the core-excited negative-ion potassium states and the excited states of atomic argon is noted.