Top: ionization rate coefficients from fits to our experiments and theoretical data (see Fig. 2). Horizontal orange and brown lines indicate temperature ranges where Fe XXV and Fe XXVI exceed 10% (dotted) and 30% (solid) of the ion fraction in equilibrium. Bottom: ratio of ionization rate coefficients to the recommended values of Urdampilleta et al. (2017), showing agreement and deviations across models: DWBE (purple), DWEA (orange), RDW (blue), CCC (gray dash-dot), RCCC (red), FAC distorted wave (green), DWBA (dashed pink), present experimental work (solid black), and its 1σ uncertainty band (dotted black).