Diffusion-coefficient ratios [D] ₄/D (gray lines) and [D] ₃/D (black lines) drawn versus the electron temperature T_e and the electron density n_e. The used densities are n_e = 10⁰ cm^-3 (no symbol), n_e = 10² cm^-3 (diamonds), and n_e = 10⁴ cm^-3 (squares). The six panels show a) m₁; b) m₂; c) m₃; d)m₄ (solid) and m₅ (dotted); e) m₆; f) m₇. The vertical gray lines indicate T_e = 4.2 × 10⁵K.