B-SplineR-matrix calculations for the spin asymmetry function in electron-impact excitation of argon and krypton

We have used the B -spline R -matrix method with non-orthogonal orbitals to perform new calculations for the spin asymmetry function S A , which determines the left–right asymmetry in the differential cross section, for electron-impact excitation of the (3p 5 4s) 3,1 P 1 states in argon and all four (4p 5 5s) states in krypton. Using non-relativistic one-electron orbitals, relativistic effects were accounted for perturbatively through terms of the Breit–Pauli Hamiltonian. In contrast to all previous theoretical attempts, we finally obtain good agreement with the benchmark measurements performed by Dümmler et al ( 1995 J. Phys. B: At. Mol. Opt. Phys. 28 2985 ).