Fully relativistic cross-sections for electron collisions with very highly stripped ions

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Lowest order quantum electrodynamics has been applied to calculate cross-sections for excitation and ionisation of very highly ionised heavy atoms by electron impact. Details of the theoretical method used are given by Pindzola et al. [Phys. Rev. A 40 (1989) 4941] and Moores and Pindzola [Phys. Rev. A 42 (1990) 5384] and a summary is given in Section 2. Starting from the two Feynman diagrams representing direct and exchange scattering respectively, fully relativistic expressions for the cross-sections are derived. The method has been applied to two separate electron impact processes: the excitation of 2s→2p (j=1/2,j=3/2) transitions in Li-like U and Hg ions; and K-shell ionisation of heavy atoms.