Contour diagrams showing the remaining flux fraction of the intercombination y and forbidden z emission lines of O vii and Fe xxv triplets, after intrinsic line absorption by the O vi and Fe xxiv ions (including fluorescent emission) as a function of and σ_v. The green vertical lines in each panel indicate N_crit, which is the critical Li-like ion column density limit corresponding to continuum optical depth τ_cont = 1 at the He-like triplet for CIE (dashed vertical line) and PIE (solid vertical line) plasma cases.