The dielectronic recombination excitation function for He-like ${\mathrm{Ni}}^{26+}$ ions has been measured. The ${\mathrm{Ni}}^{26+}$ ions were created and held in an electron beam ion trap, and K x rays were detected. Several features were observed, including resonant excitation of ${\mathrm{Ni}}^{26+}$ x rays and the transition from dielectronic recombination to direct excitation at threshold. The cross section for the KLL dielectronic recombination resonances relative to radiative recombination has been measured, and agrees with theoretical cross sections calculated using the multiconfiguration Dirac-fock model.

• Received 5 December 1988

DOI:https://doi.org/10.1103/PhysRevLett.62.2104