Possible molecular hydrogen formation mediated by the inner and outer carbon atoms of typical PAH cations

Hydrogen dissociation of naphthalene cations: a theoretical study

“…An alternative catalytic mechanism proposed by Bauschlicher (1998Bauschlicher ( , 1999 and Hirama et al (2004) involves the addition of a H atom to the PAH + cation giving (PAH)H + cation. The arrival of another H atom leads to the formation of H 2 and to release of the initial PAH + cation.…”

“…Competition between the H and H 2 channels is of particular interest because several authors have put forward observational evidence that PAHs can play an important role in the formation of H 2 in photodissociation regions (Joblin et al 2000;Habart et al 2004). The catalytic formation of H 2 has also been theoretically predicted from the collision of PAH + (Bauschlicher 1998;Hirama et al 2004) …”

Catalyzed Routes to Molecular Hydrogen Formation and Hydrogen Addition Reactions on Neutral Polycyclic Aromatic Hydrocarbons under Interstellar Conditions

“…However, the calculations showed that even the smallest PAH cation, C 10 H þ 8 (napthalene), was able to stabilize radiatively in an H addition reaction. Hirama et al (2004) showed that not only the edge sites but also carbon atoms in center sites could bind an H atom and thereby act as catalytic sites for H 2 formation via abstraction reactions. In this work we present calculations on competing addition and abstraction reaction mechanisms which lead to the formation of H 2 on and to the superhydrogenation of the neutral PAH molecule coronene.…”

Formation of H2 from internally heated polycyclic aromatic hydrocarbons: Excitation energy dependence

“…More recently, it has been suggested that Polycyclic Aromatic Hydrocarbon (PAH) molecules may play important roles as catalytic centers in the formation of H 2 . [5][6][7][8][9][10][11] PAHs are believed to be omnipresent in the ISM as the carriers of the strong infrared emission features from galactic and extragalactic objects. [12][13][14][15] One proposed route involves the capture of a free hydrogen atom by a neutral 16 or singly charged PAH, 5,7,8 which gives an aliphatic carbon.…”