Letting all three parameters vary according to a random normal distribution with standard deviation given by the error bars, we arrive at Nat = 61  38 for 10 6 random systems. This mean number of atoms agrees with the previous calculations. Nevertheless, as we can see in the density plot at the bottom of Figure , it also indicates that a large variety of possible molecular systems falls within the parameter constraints. The figure also shows a few PAH molecules ranging from small to large sizes. Except for naphthalene neutral and cation, they all fall in the high-density region, as we would expect from PAH mixtures that should occur in the interstellar media. This analysis considers only molecules returning ground state via radiationless pathways. If they fluoresce, the peak temperature after re-equilibration in the ground state should correspond to a vibrational excess discounting the energy of the emitted photon.