The results of the one-dimensional Monte Carlo model for ζ described in Sect. 2 in terms of A_V. The solid red, dashed green, and dotted blue lines derive from the flux-spectra of Nath & Biermann (1994), Hayakawa et al. (1961), and Spitzer & Tomasko (1968), respectively. These lines fit the averaged result of dozens of iterations of the Monte Carlo model. The results from a single Monte Carlo run using the flux-spectrum of Hayakawa et al. (1961) are included (pink dotted) in order to show error.