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Center for Nonlinear Studies |
R-matrix theory has been applied to atomic collision processes since the pioneering work of P. G. Burke and his colleagues at Queens University of Belfast in the early 1970s. In recent years, the development of efficient parallel R-matrix programs has made it possible to apply this method to much more complex targets and to include the target continuum in the close-coupling expansion. We will present a brief overview of R-matrix theory and the parallel R-matrix programs that have been developed as part of a collaborative effort at Rollins College, the University of Strathclyde in Scotland, and Auburn University. We will then consider the application of the R-matrix with pseudo-states (RMPS) method to the calculation of electron-impact ionization and excitation for neutral and low charge-state ions. In addition, we will present Dirac R-matrix calculations of electron-impact excitation of low charge-state ions of iron as well as highly ionized species of current interest to research on magnetically confined fusion plasmas. Finally, we will show the results of an RMPS calculation of direct single-photon double photoionization of neutral magnesium.