Summed abundance for all cluster sizes (coronene: solid lines, ovalene: dotted lines) relative to the ISM. All clusters that desorbed, dissociated, and then experienced C₂H₂ loss are marked in black. The resulting gas-phase monomer fraction resulting from the desorption and subsequent dissociation by X-rays is shown in red. Since most PAHs are adsorbed in the form of clusters with more than 25 molecules, the adsorbed fraction of PAHs hardly changes at all.