PAHs and the Chemistry of the ISM

This review describes five categories of the reactions of polycyclic aromatic hydrocarbons, including photochemistry, electron attachment/detachment, recombination processes, radical reactions, and ion-neutral chemistry. For each class of reaction, an overview of the studies and their general results are presented, as well as references to the literature. The thermochemistry of PAHs and relevant species is described, including bond dissociation energies, ionization energies, electron affinities, basicities, acidities, and the interrelationships of these quantities. Modeling of the chemistry of PAHs and their ions is discussed for both diffuse and dark clouds. The role of PAH cations in the catalytic formation of molecular hydrogen is considered. Finally, this review concludes with a discussion of current challenges in the chemical characterization of PAHs, and a perspective for future studies.