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.

Recent advances in the experimental and theoretical investigation of the excitation of the (np5(n + 1)s2)2P3/2,1/2 autoionizing states in alkali atoms is reported. These include a joint theoretical and experimental investigation of the lowest (5p56s2)2P3/2 autoionizing state in Cs, for which the ejected-electron excitation function was measured at an incident-electron energy resolution of 0.2 eV for impact energies up to 4 eV above the threshold, an improved R-matrix calculation for electron-impact excitation of the (3p54s2)2P3/2,1/2 leading autoionizing doublet in K, and a theoretical study of the inner-shell photodetachment of the Na− ion. The calculations for sodium and potassium were performed by employing a B-spline R-matrix (close-coupling) code in the semi-relativistic Breit–Pauli approximation, whereas the calculations for caesium were carried out with a new fully relativistic Dirac B-spline R-matrix program. All excitation functions reveal pronounced near-threshold resonance features, which were analysed and tentatively assigned on the basis of the present calculations.

The ejected-electron excitation functions of the J = 3/2, 1/2 components of the (2p 5 3s 2 ) 2 P leading autoionizing doublet in sodium atoms were measured at an incident electron energy resolution of 0.25 eV over the incident electron energy range from the lowest excitation threshold up to 36 eV. On the basis of 56-state R-matrix (close-coupling) calculations, the observed strong near-threshold structures were classified as negative-ion resonances with likely configurations 2p 5 3s 2 3p and 2p 5 3s3p 2 .

The ejected-electron excitation functions of the lowest-lying autoionizing states (1s2s2) 2S, (1s2s2p) 4P1/2,3/2, 1s(2s2p 3P) 2P and 1s(2s2p 1P) 2P in lithium atoms have been measured for the first time at the magic angle of 54.7°. The measurements have been performed at the energy resolution of 0.4 eV over the electron impact energy range from the excitation thresholds up to 600 eV. In all excitation functions the strong resonance structures are revealed just above the excitation thresholds and in the high-impact energy region. The near-threshold structures are tentatively assigned to the shape resonances and autodetaching states of the lowest-lying 1s2s2p2, 1s2s2p3s, 1s2s2p3p and 1s2p3 Li- configurations. Above 61 eV the radiative cascade transitions from the upper autoionizing levels are considered to interpret the data. The results obtained point out the important role of negative-ion resonances in the near-threshold excitation of autoionizing states in lithium atoms.

The cascade population of the (3p54s2)2P3/2, 1/2 lowest autoionizing levels in potassium has been studied to shed light on recent experimental observations of a noticeable enhancement in the cross sections around 22 eV incident electron energy. The ejected-electron excitation functions of both levels have been re-measured in the range of 20–28 eV, and calculations of the decay parameters for the 3p54s4p levels have been performed in single-configuration Hartree–Fock and configuration-interaction approaches. The analysis of these results, together with other available experimental and theoretical data on the 3p subshell excitation in potassium, revealed a relatively small contribution (<3%) of radiative transitions from the (3p5 4s4p1P)2P, 2D levels to the apparent (including cascade contributions) excitation cross sections of the (3p54s2)2P3/2, 1/2 levels. However, the decay of negative-ion resonances associated with the upper doublets in the 3p54s4p and 3p53d4s configurations may lead to a significant cascade population of the (3p54s2)2P3/2, 1/2 levels in the impact energy region 21–28 eV.