Upper panel: spectrum of the local UV-visible radiation field in NGC 7023-NW at 42″ (A_V = 0) from the star, compared to the rates of dissociation and IR emission of the circumovalene molecule C₆₆H₂₀. Lower panel: the internal energy of C₆₆H₂₀ (red histogram) computed with our model in steady state, in the radiation field shown in the upper panel. The black histogram shows the distribution of internal energies of C₆₆H₂₀ molecules prior to dissociation. The vertical dashed lines show the 13.6 eV limit, emphasising that dissociation is dominated by multiphoton events.