Fig. 2. The combined photoelectric and Compton cross-sections relative to H as a function of energy, scaled by E/10 keV for clarity of presentation. (a) The elements H to Fe that are at least as abundant as Fe (H, He, C, N, O, Ne, Mg, Si, Fe) (b) the same elements as in (a) with solar abundance of H and He reduced by 10 (c) The precursor dust combination and (d) the element Fe.