Resonances in the collision strength for electron excitation of the 11S-23S and 11S-23P0transitions in O VII

The R-matrix method is used to calculate the collision strengths for the electron excitation of the ground state of O VII to the 2 3 S and 2 3 P 0 states. Results are presented for calculations in which the five lowest states (all n=1 and n=2 states) were included as target states and also for calculations in which the eleven lowest states (all n=1, n=2 and n=3 states) were included. The five-state calculations for the 1 1 S-2 3 S transition give many series of large resonances of the form 1s2lnl' converging to the other n=2 thresholds. For the eleven-state calculations but for the eleven-state calculations there are also significant resonances of the form 1s3lnl' converging to the n=3 thresholds. Resonance effects are quite small for the 1 1 S-2 3 P 0 transition.