B-spline R-matrix with pseudo-states calculations for electron-impact excitation and ionization of calcium.

The \hbox{B-spline} R-matrix with Pseudo-States method [1,2] was employed to treat electron collisions with calcium atoms. Predictions for elastic scattering, excitation, ionization, and ionization-excitation were obtained for all transitions between the lowest 39 states of Ca in the energy range from threshold to 100~eV. The accuracy of the results was checked by comparing them with available experimental data and testing different approximations with increasing number of coupled states. The largest scattering model included 483 states, most of which were pseudo-states that simulate the effect of the high-lying Rydberg continuum and, most importantly, the ionization continuum on the results for transitions between the discrete states of interest. This effect is particularly strong at ``intermediate'' incident energies of a few times the ionization threshold. The dataset generated from the largest model is estimated to be accurate to within a few percent for the cross sections of relevance for plasma modelling. [1] O.~Zatsarinny, Comp.\ Phys.\ Commun.~{\bf 174} (2006) 273. [2] O.~Zatsarinny and K.~Bartschat, J.~Phys.\ B~{\bf 46} (2013) 112001.