Autoionization Spectra of Magnesium (Mg i, MG ii, and MG Iii) in the 50- to 110-eV Energy Range

A total of 68 resonances have been identified in the absorption spectrum of magnesium; 24 of them belong to the neutral atom and were almost entirely classified previously. In this paper we report for the first time 38 lines of singly ionized magnesium and a Rydberg series with six members corresponding to Mg iii levels. All upper levels involve inner-shell excitation of a 2p electron for Mg I and Mg ii transitions and of a 2s electron for Mg iii. Theoretical calculations involve extensive discussions of the electron coupling schemes for the Mg I and Mg ii levels which do not retain an LS character because of the large spin-orbit interaction of the core. Subject headings: autoionization - line identifications - spectra, laboratory - spectra, ultraviolet.