Effects of hydrogen dissociation on the infrared emission spectra of naphthalene: theoretical modeling

The IR emission spectroscopy of naphthalene and its singly- and doubly-dehydrogenated radicals has been modeled using kinetic Monte Carlo simulations, taking into account the various relaxation pathways of radiative emission and hydrogen loss. Our modeling relies on quantum chemistry ingredients that were obtained from dedicated calculations based on density functional theory, including explicitly anharmonicity contributions. Our results show that the fragmentation products significantly contribute to the overall IR emission spectrum, especially to the intensity ratios between bands. Owing to the likely presence of polycyclic aromatic hydrocarbons in the interstellar medium, these findings are particularly relevant in the astrophysical context.