Steady-state calculations of fractional abundances and abundance ratios. All the input parameters except S/H are the same as in Fig. B.2. Horizontal blue lines correspond to the observed values and their uncertainty. Vertical green lines indicate the estimated value of the sulfur elemental abundance, S/H = 6 × 10^-7. The solid black line represents our best model fit, ζ_H2 = 4 × 10^-17 s^-1. The dashed blue, black, and red lines correspond to ζ_H2 = 1, 4 and 10 × 10^-17 s^-1, respectively.