Electron impact ionisation results by the Z=∞ method

The procedure given previously by Golden and Sampson (1977) for obtaining ionisation results for highly charged ions with finite Z from the scaled results for hydrogenic ions with Z= infinity is modified slightly and a prescription is given for including the effects of lowered ionisation potentials occurring in dense plasmas. The results by this approach are then compared with various experimental, theoretical and semi-empirical results for ionisation of He-like, Li-like and Be-like ions with Z/N in the range 2<or=Z/N<or approximately=3, where N is the number of bound electrons per ion. It appears that, for Z/N in this range, the method gives results at least as accurate as those obtained by the exchange classical impact-parameter method and more accurate than the other available theoretical and semi-empirical results. The accuracy of the approach should improve as Z/N is increased.