Dominant hydrogenation state as a function of PAH size and position in the NGC 7023 NW PDR, without reactivity (upper panel) or with a rate of 5 × 10^-13 cm³ s^-1 (middle panel) for the reaction between PAH cations and H₂. The points represent the parameters for which models were computed. Red, yellow, and green represent carbon clusters, normally hydrogenated PAHs, and superhydrogenated PAHs (limited to one extra H-atom), respectively. Lines delimiting the different domains were interpolated to guide the eye and should be considered with caution. The power per unit of volume P_AIB emitted in the mid-IR domain by PAHs and carbon clusters as a function of their position is shown in the lower panel, and is also overlaid as a brightness scale to the upper and middle panels. The variation observed between A_V = 0 and 0.2 reflects the variation of n_H (see Fig. 2).