Dielectronic recombination of boronlike argon

We present measurements and calculations of Delta n=0 dielectronic recombination resonances of boronlike argon between 0.2 and 6 eV. A storage ring equipped with an electron cooler was used for the measurements. Methods employed to reduce the electron energy distribution and improve the accuracy of resonance energy measurements have yielded an energy resolution of 30 meV full width at half maximum at low energies, and an energy uncertainty better than 30 meV. The high energy resolution results from the use of an adiabatic expansion technique to reduce the transverse electron energy distribution. The improved accuracy in energy determinations is achieved through the inclusion of variations in the ion velocity, which occur during scans of the electron velocity, in the relative velocity transformations. Calculations of the resonance strengths and energies were made using two different methods, multiconfiguration Dirac-Fock and multiconfiguration Breit-Pauli approximations. A comparison of the experimental data to the calculations shows fair agreement in both the spectral features and integrated intensities above 3 eV. However, poor agreement is found below 3 eV.