Comparison of IR emission and photodissociation rates as a function of internal energy of the PAH. The rates determined for coronene derivatives are shown in black, while the rates for circumcoronene and circumcircumcoronene are shown in blue and red respectively, following the color scheme of Fig. 4. The grey vertical lines show the activation energies assumed listed in Table 2. The left panel shows the rates for the first dehydrogenated state of each parent molecule in their neutral state (C₂₄H, C₅₄H and C₉₆H), in order to exemplify the rates for molecules with an odd number of H atoms. The middle panel shows the rates for the parent neutral molecules, illustrating the H and H₂-loss rates for PAHs with an even number of H atoms. The right panel shows the rates for the first superhydrogenated state of the neutral molecules (i.e., C₂₄H, C₅₄H, and C₉₆H) for which no direct H₂-loss is considered. IR emission rates as a function of internal energy, k_IR(E), have been calculated using the IR cross sections of each molecule whenever available (see Appendix A). For C₂₄H and C₉₆H we have assumed the intrinsic frequencies of the parent molecules.