Efficiencies of H₂ formation from PAHs. The left panel shows the efficiencies of H₂ formation through Eley-Rideal abstraction from superhydrogenated species as a function of G₀/n(H). Estimates for circumcoronene and circumcircumcoronene superhydrogenated species are shown in blue and red, respectively. The efficiencies have been derived for neutrals and anions, since these are the charge states at which superhydrogenated species can be found according to our model. Two gas temperatures have been assumed as a reference. The right panel shows the efficiencies of H₂ formation from photodissociation of PAHs. The efficiencies have been derived for neutral coronene at G₀=10, and Z> 0 circumcoronene at G₀=10³. We have considered different G₀ values due to the different dehydrogenation behaviour of the species in the G₀-n(H) parameter space (see Fig. 9). As it can be derived from the figure, efficiencies stay below 1% for both mechanisms.