Study of Characteristics of AC Arc Discharges on Polluted Insulator Surfaces

Abstract

Recent advances in the experimental and theoretical investigation of the excitation of the (np 5 (n + 1)s 2 ) 2 P 3/2,1/2 autoionizing states in alkali atoms is reported. These include a joint theoretical and experimental investigation of the lowest (5p 5 6s 2 ) 2 P 3/2 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 (3p 5 4s 2 ) 2 P 3/2,1/2 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.