Molecular hydrogen formation, interstellar

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... 

Mennella, V. 2009. Laboratory studies of the hydrogen-carbon grains interaction Application to the evolution of the interstellar carbonaceous matter and to molecular hydrogen formation. Astronomical Society of the Pacific Conference Series, 414(Cosmic Dust) 428-437. 

Peretz HB, Lederhendler A, Biham O, VidaJi G, Li L, Swords S, Congiu E, Roser J, Manico G, Brucato JR, Pirronello V. (2007) Molecular Hydrogen Formation on Amorphous Silicates under Interstellar Conditions Astrophys. J. 661 L163-L166. 

The rate coefEcients for this reaction, which have been presented at a conference, are compared in Fig. 3.24 with those for the reverse reaction which also has been mentioned above. A detailed discussion of all results together with a critical analysis of the kinematics is in preparation. A question which is related to reaction (3.43) is whether catalytic cycles such as XY+ + H —> XYH+ followed by XYH+ + H —> XY+ + H2 can contribute to the formation of molecular hydrogen under interstellar conditions. 

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

The cycle of birth and death of stars that is initiated by population III stars constantly increases the abundance of heavy elements in the interstellar medium, a crucial prerequisite for terrestrial (rocky) planet formation and subsequently for the origin of life (75). Metals dispersed in the interstellar gas or incorporated into micron-sized dust particles and molecules like CO and water, have the ability to cool the interstellar gas much more efficiently than molecular hydrogen does for population III stars. These elements and molecules are also excited through atomic and molecular collisions and their return to lower lying energy levels releases energy via far-infrared and sub-millimeter radiation below... 

The reaction of N ions with molecular hydrogen to form NH ions was thought to initiate ammonia formation in interstellar clouds. Recently several experimental studies, either at very low temperature (Marquette et al, 1985b Luine and Dunn,... 

Although the major interstellar reaction that occms on the surfaces of dust particles is the formation of molecular hydrogen, more complex molecules are also thought to be formed in this maimer. 

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,...

In the laboratory, the study of the properties of pure polyynes and poly-cumulenes is inhibited because of their extreme reactivity with oxygen and the formation of cross linked chains. In space, refractory dust made of silicates or carbonaceous material are formed in the atmosphere of evolved stars and released into the interstellar medium (ISM). In dense molecular clouds ( Hydrogen > 10 cm, 10-20 K) atoms and molecules that... 

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