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 3sεl → 3pnl, 3dnl (Δn = 0) resonances and a single 3sεl → 4s4p (Δn = 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.