FORBIDDEN TRANSITIONS IN ONE-ELECTRON AND 2-ELECTRON NICKEL

We describe measurements of the lifetimes of metastable states in one- and two-electron nickel ions. The 2 S-1(1/2) level in one-electron ni ckel was found to have a lifetime of 217.1(1.8) ps, in agreement with a theoretical calculation of 215.45 ps. The lifetimes of the 2 S-1(0) and 2 P-3(2) levels in two-electron nickel were found to be 156.1(1.6) and 70(3) ps, respectively, in agreement with the theoretical results of 154.3(0.5) and 70.6 ps. We also studied the phenomenon of hyperfin e quenching of the He-like 2 P-3(0) level by comparing decay curves fo r the isotopes Ni-61 and Ni-58. The lifetime of the 2 P-3(0) level in Ni-61(26+) was found to be 470(50) ps, in agreement with a theoretical prediction. The measurements were carried out using the beam-foil tim e-of-flight technique with a fast beam of highly charged nickel ions. We discuss the handling of systematic effects in the measurements, inc luding the study of yrast cascades following the beam-foil interaction .