6 Comparison with the work of others

Of the papers listed in Table 1 those by Bhatia & Mason (1981, 1986); Zhang & Sampson (1992); Chen & Ong (1998) deal with the transitions in Table 9. These workers all used distorted wave approximations which do not take account of resonance effects. We give some graphical comparisons which show that there is fairly good agreement between our background collision strengths and the distorted wave results. Only for the forbidden transitions 1-9 (electric quadrupole) and 1-10 (electric monopole), which involve 2 electron jumps, are the differences more noticeable. Figure 6 shows that Zhang & Sampson's (1992) relativistic distorted wave collision strength ${\sl \Omega}(1 - 9)$ is significantly lower than ours. We can see no obvious explanation for this. Chen & Ong's (1998) results, which came to our attention as the present investigation was drawing to a close, are in better agreement with our data for this transition (see Fig. 6).