Effective collision strength (Υ_lu) at 5000 K for forbidden transitions of Ni III versus the product of the statistical weights of the lower and upper levels. Different symbols are used for transitions corresponding to wavelengths < 10 μm (filled circles) or ≥10 μm (open diamonds). We also highlight transitions among the first ten levels (see Table F.1). Overplotted are the approximations of Axelrod (1980) for the two wavelength regimes. The Υ_lu values deviate by more than one order of magnitude for many transitions (including for some among low-lying levels).