OP monochromatic cross-sections (in atomic units) of H, He, C, N, O and Fe elements for lgT = 4.35 K and lgN_e = 15.0 corrected for abundance parameters of the elements, σ_kf_k. Panel a) shows the cross-sections for H (thick line) and He (dashed line). Panel b) shows data for C, N and O elements in comparison with the dominant absorber of H. Panel c) shows the same as panel b), but for Fe.