Effective collision strengths of fine-structure transitions in Fe X, Fe XI, and Fe XIII

Electron excitation collision strengths for fine-structure transitions in F e x, Fe xI, and Fe xIII are calculated using full Breit-Pauli R-matrix appr oach. We included 49 fine-structure levels of Fe x, 38 finestructure levels of Fe xI, and 26 fine-structure levels of Fe xIII in our scattering calcul ations. These levels are represented by configuration-interaction wave func tions. The relativistic effects are included in the Breit-Pauli approximati on via one-body mass correction, Darwin, and spin-orbit interaction terms i n the scattering equations. Rydberg series of resonances converging to the excited state thresholds are explicitly included in the calculations. The e ffective collision strengths are determined by integrating collision streng ths and assuming a Maxwellian distribution of electron energies.