| Summary: | There is overwhelming demand for accurate atomic data for Chromium 11, critical in the analysis of a broad range of astrophysical bodies. This thesis is the largest calculation undertaken for the electron-impact excitation of Cr 11. The target model, determined using CIV3, consists of the 3 configurations 3d5, 3d~s and 3d44p corresponding to a 280 jj-Ievel, 1932 coupled channel problem. A further 7 Configuration Interaction terms are included along with a 4d pseudo orbital. The scattering calculation internal region was completed using RMATRX 11 plus the module FINE to account for relativistic effects and then PSTGF is used for the external region. Collision strengths and Maxwellian averaged effective collision strengths are calculated and comparisons are made with the work of Bautista et al. (2009). A mixed bag of results are observed with good agreement across many transitions but significant differences for others. The Cr 11 model is also used with RMATRX I in a full Breit-Pauli Hamiltonian treatment. Code limitations force this calculation to be completed for a limited number of In partial ) waves. Comparisons are made for a number of transitions and excellent agreement is found between the results from these two very different codes and methodologies. This strong correlation provides a stringent test between an LS-coupling with transformation approach to include relativistic effects and a full Breit-Pauli treatment. This work was undertaken in collaboration with Auburn University, Alabama, thanks to the Caldwell scholarship. Work has also been started on the development of CIV3 to make use of coefficients of fractional grandparentage. Adopting the associated theory to extract two electrons from the same subshell dramatically decreases the time taken in large atomic structure calculations. Finally, I present utility codes that have significantly increased efficiency and have proven useful in the Cr 11 calculation and analysis of the results.
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