THE DOUBLE-IONIZATION OF CS-RESOLVED ELECTRONS( AND SR+ BY ENERGY)

Absolute cross sections for the double ionization of Cs+ and Sr+ by en ergy-resolved electrons have been measured from their threshold energi es to 130 and 180 eV, respectively. The double ionization cross sectio n of Cs+ displays a broad rise beginning at about 80 eV which reaches a peak at around 125 eV. This peak can be attributed to a giant resona nce as a result of reactions involving the excitation or ionization of a 4d electron followed by autoionization. Many steps and resonant pea ks are observed, some of which can be exclusively assigned to resonant recombination followed by triple autoionization (RETA). There is no e vidence of a giant resonance in the double ionization of Sr+, but a we alth of structure, due to autoionizing processes, is displayed in the cross section. The cross section of Sr+ is concave at threshold.