Molecular hydrogen formation on amorphous silicates under interstellar conditions

H. B. Perets, A. Lederhendler, O. Biham, G. Vidali, L. Li, S. Sworos, E. Congiu, J. Roser, G. Manicó, J. R. Brucato, V. Pirronello

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Abstract

Experimental results on the formation of molecular hydrogen on amorphous silicate surfaces are presented for the first time and analyzed using a rate equation model. The energy barriers for the relevant diffusion and desorption processes are obtained. They turn out to be significantly higher than those obtained earlier for polycrystalline silicates, demonstrating the importance of grain morphology. Using these barriers, we evaluate the efficiency of molecular hydrogen formation on amorphous silicate grains under interstellar conditions. It is found that unlike polycrystalline silicates, amorphous silicate grains are efficient catalysts of H2 formation within a temperature range that is relevant to diffuse interstellar clouds. The results also indicate that the hydrogen molecules are thermalized with the surface and desorb with low kinetic energy. Thus, they are unlikely to occupy highly excited states.

Original languageEnglish (US)
Pages (from-to)L163-L166
JournalAstrophysical Journal
Volume661
Issue number2 II
DOIs
StatePublished - Jun 1 2007

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Keywords

  • Dust, extinction
  • ISM: molecules
  • Molecular processes

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Perets, H. B., Lederhendler, A., Biham, O., Vidali, G., Li, L., Sworos, S., Congiu, E., Roser, J., Manicó, G., Brucato, J. R., & Pirronello, V. (2007). Molecular hydrogen formation on amorphous silicates under interstellar conditions. Astrophysical Journal, 661(2 II), L163-L166. https://doi.org/10.1086/518862