Title:
The Formation of Molecular Hydrogen on Silicate Dust Analogs: The Rotational
Distribution
Authors:
Gavilan, L.; Lemaire, J. L.; Vidali, G.; Sabri, T.; Jæger, C.
Affiliation:
AA(; lisseth.gavilan@obspm.fr), AB(LERMA, UMR 8112 du CNRS, de l'Observatoire de Paris et de l'Université de Cergy Pontoise, 5 mail Gay Lussac, F-95000 Cergy
Pontoise Cedex, France), AC(Visiting Professor. Permanent address: Syracuse
University, Physics Department, Syracuse, NY 13244-1320, USA.), AD(Laboratory
Astrophysics and Cluster Physics Group of the Max Planck Institute for Astronomy at the Friedrich Schiller University Jena.), AE(Laboratory Astrophysics and Cluster Physics Group of the Max Planck Institute for Astronomy at the Friedrich Schiller University Jena.)
Publication:
The Astrophysical Journal, Volume 781, Issue 2, article id. 79, 13 pp. (2014). (ApJ Homepage)
Publication Date:
02/2014
Origin:
IOP
Astronomy Keywords:
astrochemistry, dust, extinction, ISM: molecules, molecular processes
DOI:
10.1088/0004-637X/781/2/79
Bibliographic Code:
2014ApJ...781...79G
Abstract
Our laboratory experiments continue to explore how the formation of molecular
hydrogen is influenced by dust and how dust thereby affects hydrogen molecules
adsorbed on its surface. In Sabri et al., we present the preparation of nanometer-
sized silicate grain analogs via laser ablation. These analogs illustrate extremes in
structure (fully crystalline or fully amorphous grains), and stoichiometry (the
forsterite and fayalite end-members of the olivine family). These were inserted in
FORMOLISM, an ultra-high vacuum setup where they can be cooled down to ~5 K.
Atomic beams are directed at these surfaces and the formation of new molecules is
studied via REMPI(2+1) spectroscopy. We explored the rotational distribution (0 <= J'' <= 5) of v'' = 0 of the ground electronic state of H2. The results of these
measurements are reported here. Surprisingly, molecules formed and ejected from
crystalline silicates have a cold (T rot ~ 120 K) rotational energy distribution, while
for molecules formed on and ejected from amorphous silicate films, the rotational
temperature is ~310 K. These results are compared to previous experiments on
metallic surfaces and theoretical simulations. Solid-state surface analysis suggests
that flatter grains could hinder the "cartwheel" rotation mode. A search for hot
hydrogen, predicted as a result of H2 formation, hints at its production. For the first
time, the rotational distribution of hydrogen molecules formed on silicate dust is
reported. These results are essential to understanding the chemistry of
astrophysical media containing bare dust grains.
{
"status": "new",
"changetime": "2019-02-04T13:07:06Z",
"_ts": "1549285626580696",
"description": "{{{\nTitle:\t\nThe Formation of Molecular Hydrogen on Silicate Dust Analogs: The Rotational \nDistribution\nAuthors:\t\nGavilan, L.; Lemaire, J. L.; Vidali, G.; Sabri, T.; J\u00e6ger, C.\nAffiliation:\t\nAA(; lisseth.gavilan@obspm.fr), AB(LERMA, UMR 8112 du CNRS, de l'Observatoire de Paris et de l'Universit\u00e9 de Cergy Pontoise, 5 mail Gay Lussac, F-95000 Cergy \nPontoise Cedex, France), AC(Visiting Professor. Permanent address: Syracuse \nUniversity, Physics Department, Syracuse, NY 13244-1320, USA.), AD(Laboratory \nAstrophysics and Cluster Physics Group of the Max Planck Institute for Astronomy at the Friedrich Schiller University Jena.), AE(Laboratory Astrophysics and Cluster Physics Group of the Max Planck Institute for Astronomy at the Friedrich Schiller University Jena.)\nPublication:\t\nThe Astrophysical Journal, Volume 781, Issue 2, article id. 79, 13 pp. (2014). (ApJ Homepage)\nPublication Date:\t\n02/2014\nOrigin:\t\nIOP\nAstronomy Keywords:\t\nastrochemistry, dust, extinction, ISM: molecules, molecular processes\nDOI:\t\n10.1088/0004-637X/781/2/79\nBibliographic Code:\t\n2014ApJ...781...79G\nAbstract\n\nOur laboratory experiments continue to explore how the formation of molecular \nhydrogen is influenced by dust and how dust thereby affects hydrogen molecules \nadsorbed on its surface. In Sabri et al., we present the preparation of nanometer-\nsized silicate grain analogs via laser ablation. These analogs illustrate extremes in \nstructure (fully crystalline or fully amorphous grains), and stoichiometry (the \nforsterite and fayalite end-members of the olivine family). These were inserted in \nFORMOLISM, an ultra-high vacuum setup where they can be cooled down to ~5 K.\n Atomic beams are directed at these surfaces and the formation of new molecules is\n studied via REMPI(2+1) spectroscopy. We explored the rotational distribution (0 <= J'' <= 5) of v'' = 0 of the ground electronic state of H2. The results of these \nmeasurements are reported here. Surprisingly, molecules formed and ejected from\n crystalline silicates have a cold (T rot ~ 120 K) rotational energy distribution, while\n for molecules formed on and ejected from amorphous silicate films, the rotational\n temperature is ~310 K. These results are compared to previous experiments on \nmetallic surfaces and theoretical simulations. Solid-state surface analysis suggests\n that flatter grains could hinder the \"cartwheel\" rotation mode. A search for hot \nhydrogen, predicted as a result of H2 formation, hints at its production. For the first\n time, the rotational distribution of hydrogen molecules formed on silicate dust is\n reported. These results are essential to understanding the chemistry of \nastrophysical media containing bare dust grains.\n}}}",
"reporter": "gary",
"cc": "",
"resolution": "",
"time": "2014-01-21T02:38:03Z",
"component": "atomic/molecular data base",
"summary": "H2 formation pumping",
"priority": "good to do",
"keywords": "",
"version": "trunk",
"milestone": "no milestone",
"owner": "nobody",
"type": "enhancement"
}
reported by: @CloudyLex
Migrated from https://www.nublado.org/ticket/274