Hydrogen, interstellar formation

Fig. 1. Interstellar formation scheme illustrating the CH, CH, C H and higher hydrocarbon cycle. The left side of the reaction cycle pertains to tenous clouds (Uj, 100 cm ), whereas the right hand side is more appropriate to areas where is present, i.e. dense molecular clouds (n 10 -10 cm" ). The thick arrows indicate assumed preferential reaction paths leading to the higher order hydrocarbons. The following processes are involved (v, e) photoionization (v, H) photodissociation (e, v) radiative recombination (H) (Hj, v) radiative association (e, H), (e, Hj) dissociative electron recombination. (Hj, H) hydrogen abstraction reaction (C, H) charge exchange (M, M ) metal charge exchange metal = Mg, Fe, Ca, Na,...

The Potential Role Played by the Fullerene-Like Structures of Interstellar Carbon Dust in the Formation of Molecular Hydrogen in Space... 

General Aspects About Molecular Hydrogen Formation in the Interstellar Medium... 

Fullerene-Like Structures on Carbon Dust of the Interstellar Medium Their Role in Molecular Hydrogen Formation... 

Experiments with deuterated species show extensive H/D scrambling, which implies longer-lived intermediates in the reaction. Calculations at the B3LYP/6-311+G(2d,p) level suggest that the reaction pathway involves bond formation between the cycloheptatrienylidene dication and acetylene, followed by isomerization and hydrogen loss (Scheme 9). The authors of this study note the possibility of similar chemistry generating polycyclic aromatic compounds in interstellar space. 

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