2009/06/03 by Emanuele Congiu, E. Congiu, Elie Matar +7 · 2 citations
Chemistry · Physics and Astronomy · #Astrophysics and Star Formation Studies #Excited state #Fullerene Chemistry and Applications #Hydrogen #Hydrogen molecule #Interstellar cloud #Interstellar ice #Interstellar medium #Molecular cloud #Molecule #Quantum, superfluid, helium dynamics #physics.space-ph
paper · pdf · doi:10.1111/j.1745-3933.2009.00692.x
15 pages, 3 figures, to be published in MNRAS
arxiv created 2009/06/03 · openalex publication_date 2009/06/22 · arxiv updated 2015/05/13 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Abstract There has always been a great deal of interest in the formation of H2 as well as in the binding energy released upon its formation on the surface of dust grains. The present work aims at collecting experimental evidence for how the bond energy budget of H2 is distributed between the reaction site and the internal energy of the molecule. So far, the non-detection of excited nascent H2 in dense quiescent clouds could be a sign that either predictions of emission line intensities are not correct or the de-excitation of the newly formed molecules proceeds rapidly on the grain surface itself. In this Letter, we present experimental evidence that interstellar molecular hydrogen is formed and then rapidly de-excited on the surface of porous water ice mantles. In addition, although we detect ro-vibrationally excited nascent molecules desorbing from a bare non-porous (compact) water ice film, we demonstrate that the amount of excited nascent hydrogen molecules is significantly reduced no matter the morphology of the water ice substrate at 10 K (both on non-porous and on porous water ice) in a regime of high molecular coverage as is the case in dark molecular clouds.