Rate coefficients at 8000 K obtained by us compared with those calculated from the CCC calculations (Schweinzer et al. 1999, left), those of Park (1971, and those calculated using the van Regemorter formula (van Regemorter 1962). The latter is only valid for optically allowed transitions, hence the limited number of comparison points. The different symbols are for the rate coefficients corresponding to the transitions: 2s → 2p [⋄, 6708 Å], 2p → 3d [□, 6104 Å], and 2p → 3s [Δ, 8126 Å].