Spectroscopic study of Mg-like Ni by means of dielectronic recombination of stored ions

Dielectronic recombination resonances of Ni17+ that form doubly excited states in Mg-like Ni were studied in the energy range up to 6.5 eV. We observed 3sepsilonl --> 3pnl, 3dnl (Deltan = 0) resonances and a single 3sepsilonl --> 4s4p (Deltan = 1) resonance in this energy region. A relativistic many-body perturbation theory calculation was performed to predict the positions and strengths of the resonances in this region. A comparison of the experimental data with the calculation yields an overall good agreement as regards the resonance positions and strengths. The discrepancies are predominantly theoretical underestimations of the rate coefficient. The 3s(1/2)-3p(1/2) and the 3s(1/2)-3p(3/2) energy splittings have been determined from the experiment.