Cumulative column density of N₂ as a function of extinction, A_V, at an excitation temperature of 30 K. Curves are shown for several different models: dotted, dashed, and solid lines indicate n_H = 100, 300 and 1000 cm^-3, respectively; blue, green and red lines scale the radiation field by χ = 0.5, 1 and 5, respectively. The asterisk indicates half the N₂ column density and half the extinction observed by Knauth et al. (2004) in the diffuse cloud toward HD 124314.