4 Summary

Electron-impact excitation cross sections and Maxwellian-averaged effective collision strengths were determined for Fe⁷⁺ using R-matrix close-coupling theory in conjunction with multi-channel quantum defect theory and the intermediate-coupling frame transformation method. Effective collision strengths were determined for all 2926 transitions among the 77 levels of seven ground and low-lying excited configurations. Furthermore, radiative rates were determined for all dipole-allowed transitions from Breit-Pauli configuration-interaction calculations; these rates, in combination with energies and effective collision strengths, were used to construct a collisional- radiative atomic data set for Fe⁷⁺, which is now available at the ORNL Controlled Fusion Atomic Data Center internet site. The ADAS collisional-radiative modeling codes and the Fe⁷⁺ atomic data set were used to calculate equilibrium populations for all 77 LSJ levels over a range of electron temperatures and densities. Spectral intensities for ten dipole-allowed transitions in Fe⁷⁺ were then calculated to produce a single blended line ratio that provides a very useful electron temperature diagnostic.

Acknowledgements

This work was supported by the U.S. Department of Energy under Contract Nos. DE-FG02-96-ER54367 with Rollins College and DE-FG05-96ER54348 with Auburn University and by the U.K. Particle Physics and Astronomy Research Council under Grant No. PPA/G/S/1997/00783 with the University of Strathclyde.