Volume 523, November-December 2010
|Number of page(s)||12|
|Section||Atomic, molecular, and nuclear data|
|Published online||18 November 2010|
Radiolysis of H2O:CO2 ices by heavy energetic cosmic ray analogs
IP&D/UNIVAP, Av. Shishima Hifumi, 2911, São
Jose dos Campos,
2 Grupo de Física e Astronomia, CEFET/Química de Nilópolis, Rua Lúcio Tavares, 1052, CEP 2653-060, Nilópolis, Brazil
3 Centre de Recherche sur les Ions, les Matériaux et la Photonique (CEA/CNRS/ENSICAEN/Université de Caen-Basse Normandie), CIMAP – CIRIL – GANIL, Boulevard Henri Becquerel, BP 5133, 14070 Caen Cedex 05, France
4 Departamento de Física, Pontifícia Universidade Católica do Rio de Janeiro (PUC-Rio), Rua Marquês de São Vicente 225, CEP 22453-900, Rio de Janeiro, Brazil
Accepted: 3 August 2010
An experimental study of the interaction of heavy, highly charged, and energetic ions (52 MeV 58Ni13+) with pure H2O, pure CO2 and mixed H2O:CO2 astrophysical ice analogs is presented. This analysis aims to simulate the chemical and the physicochemical interactions induced by heavy cosmic rays inside dense and cold astrophysical environments, such as molecular clouds or protostellar clouds. The measurements were performed at the heavy ion accelerator GANIL (Grand Accélérateur National d’Ions Lourds in Caen, France). The gas samples were deposited onto a CsI substrate at 13 K. In-situ analysis was performed by a Fourier transform infrared (FTIR) spectrometer at different fluences. Radiolysis yields of the produced species were quantified. The dissociation cross sections of pure H2O and CO2 ices are 1.1 and 1.9 × 10-13 cm2, respectively. For mixed H2O:CO2 (10:1), the dissociation cross sections of both species are about 1 × 10-13 cm2. The measured sputtering yield of pure CO2 ice is 2.2 × 104 molec ion-1. After a fluence of 2−3 × 1012 ions cm-2, the CO2/CO ratio becomes roughly constant (~0.1), independent of the initial CO2/H2O ratio. A similar behavior is observed for the H2O2/H2O ratio, which stabilizes at 0.01, independent of the initial H2O column density or relative abundance.
Key words: astrochemistry / molecular data / solar wind / cosmic rays / ISM: molecules / planets and satellites: composition
© ESO, 2010
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