Iso-electronic trends for continuum coupling effects on the electron-impact excitation of H-like ions

We have carried out pseudo-state and non-pseudo-state R-matrix close-coupling calculations for the electron-impact excitation of the H-like ions He+, Li2+, Be3+ and B4+. Illustrative results are presented for the ns --> n's transitions since these are most affected by coupling to the continuum and highly excited states. In particular, our numerical results show that the effect of such coupling on the cross section scales roughly as 1/z, where z is the residual charge on the ion.