CE/SB ionization-stage population comparisons for H, He, Si and Fe. Upper panel of each pair: CE distribution with temperature. Lower panel of each pair: SB distribution with temperature for fixed electron density N_e = 10¹⁴ cm^-3. For lower N_e the SB curve patterns remain similar but the flanks steepen and the peaks shift leftward (about −0.05 in log (T) for tenfold N_e reduction). The first pair for hydrogen has logarithmic y-axes; the dashed curves are on the linear scales of the other panels.