Full-Relativistic B-Spline R-Matrix Calculations for Electron Collisions with Gold Atoms.

We have extended the $B$-spline $R$-matrix (close-coupling) method~[1] to fully account for relativistic effects in a Dirac-Coulomb formulation. The newly developed computer code has been applied to electron-impact excitation of the $\rm (5d^{10}6s)^2S_{1/2} \to (5d^{10}6p)^2P_{1/2,3/2}$ and $\rm (5d^{10}6s)^2S_{1/2} \to (5d^{9}6s^2)^2D_{5/2,3/2}$ transitions in Au. Our numerical implementation of the close-coupling method enables us to construct term-dependent, non-orthogonal sets of one-electron orbitals for the bound and continuum electrons. This is a critical aspect in the present problem, especially for the 5d and the 6s orbitals. Furthermore, strong core-polarization effects can be accounted for {\it ab initio\/} rather than through a semi-empirical and local model potential. Our results will be compared with recent experimental data~[2] and predictions from other theoretical approaches~[3]. [1]~O.~Zatsarinny, Comp. Phys. Commun. {\bf 174}, 273 (2006). [2]~M.~Maslov, P.J.O. Teubner, and M.J.~Brunger, private communication (2008). [3]~D.V.~Fursa, I. Bray, and R.P. McEachran, private communication (2008).