Ly α Irradiation of Superhydrogenated Coronene Films: Implications for H 2 Formation

We present the results of an experimental study of the interaction of Lyα photons with superhydrogenated coronene films. The effects of ultraviolet (UV) irradiation have been analyzed with infrared spectroscopy. The spectral changes provide evidence for UV photodestruction of the C–D bonds of the superhydrogenated coronene with a cross section of 8 ± 2 × 10−20 cm2. The comparison of our experimental result with the prediction from theoretical modeling suggests an extension of the region inside photodissociation regions where superhydrogenated coronene can survive and contribute to H2 formation. H2 formation through abstraction in superhydrogenated coronene dominates over direct H2 loss induced by UV photodestruction.