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Differential adsorption of complex organic molecules isomers at interstellar ice surfaces

Lattelais, M. ; Bertin, M. ; Mokrane, H. ; Romanzin, C. ; Michaut, X. ; Jeseck, P. ; Fillion, J.-H. ; Chaabouni, H. ; Congiu, E. ; Dulieu, F. ; Baouche, S. ; Lemaire, J.-L. ; Pauzat, F. ; Pilmé, J. ; Minot, C. ; Ellinger, Y.

Astronomy and astrophysics (Berlin), 2011-08, Vol.532, p.A12 [Periódico revisado por pares]

Les Ulis: EDP Sciences

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  • Título:
    Differential adsorption of complex organic molecules isomers at interstellar ice surfaces
  • Autor: Lattelais, M. ; Bertin, M. ; Mokrane, H. ; Romanzin, C. ; Michaut, X. ; Jeseck, P. ; Fillion, J.-H. ; Chaabouni, H. ; Congiu, E. ; Dulieu, F. ; Baouche, S. ; Lemaire, J.-L. ; Pauzat, F. ; Pilmé, J. ; Minot, C. ; Ellinger, Y.
  • Assuntos: astrochemistry ; Astronomy ; Chemical Sciences ; Earth, ocean, space ; Exact sciences and technology ; ISM: abundances ; ISM: molecules
  • É parte de: Astronomy and astrophysics (Berlin), 2011-08, Vol.532, p.A12
  • Notas: e-mail: pauzat@lct.jussieu.fr
    ark:/67375/80W-9BK3K29T-4
    dkey:10.1051/0004-6361/201016184
    bibcode:2011A%26A...532A..12L
    istex:528A41D43D926E09474E4E162A305C33524E1C6C
    publisher-ID:aa16184-10
  • Descrição: Context. Over 20 of the  ~150 different species detected in the interstellar and circumstellar media have also been identified in icy environments. For most of the species observed so far in the interstellar medium (ISM), the most abundant isomer of a given generic chemical formula is the most stable one (minimum energy principle – MEP) with few exceptions such as, for example, CH3COOH/HCOOCH3 and CH3CH2OH/CH3OCH3, whose formation is thought to occur on the icy mantles of interstellar grains. Aims. We investigate whether differences found in the compositions of molecular ices and the surrounding gas phase could originate from differences between the adsorption of one isomer from that of another at the ice surface. Methods. We performed a coherent and concerted theoretical/experimental study of the adsorption energies of the four molecules mentioned above, i.e. acetic acid (AA)/methyl formate (MF) and ethanol (EtOH)/dimethyl ether (DME) on the surface of water ice at low temperature. The question was first addressed theoretically at LCT using solid state periodic density functional theory (DFT) to represent the organized solid support. The experimental determination of the ice/molecule interaction energies was then carried out independently by two teams at LPMAA and LERMA/LAMAp using temperature programmed desorption (TPD) under an ultra-high vacuum (UHV) between 70 and 160 K. Results. For each pair of isomers, theory and experiments both agree that the most stable isomer (AA or EtOH) interacts more efficiently with the water ice than the higher energy isomer (MF or DME). This differential adsorption can be clearly seen in the different desorption temperatures of the isomers. It is not related to their intrinsic stability but instead to both AA and EtOH producing more and stronger hydrogen bonds with the ice surface. Conclusions. We show that hydrogen bonding may play an important role in the release of organic species from grains and propose that, depending on the environment, differential adsorption should not be rejected as a possible way of interpreting MEP exceptions.
  • Editor: Les Ulis: EDP Sciences
  • Idioma: Inglês
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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