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Author Bossa, Jean-Baptiste ♦ Fransen, Coen ♦ Cazaux, Stéphanie ♦ Linnartz, Harold ♦ Maté, Belén ♦ Ortigoso, Juan ♦ Pilling, Sergio ♦ Rocha, Will Robson Monteiro
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword ATOMIC AND MOLECULAR PHYSICS ♦ ASTROPHYSICS, COSMOLOGY AND ASTRONOMY ♦ COMPUTERIZED SIMULATION ♦ DEPOSITION ♦ ICE ♦ INFRARED SPECTRA ♦ INTERMEDIATE INFRARED RADIATION ♦ METHANE ♦ MIXTURES ♦ MOLECULES ♦ MONTE CARLO METHOD ♦ MORPHOLOGY ♦ POROSITY ♦ POROUS MATERIALS ♦ REFRACTIVE INDEX ♦ SOLIDS ♦ STOICHIOMETRY ♦ WATER
Abstract We use experimental mid-infrared optical constants and extended effective medium approximations to determine the porosity and the band strengths of multi-phase composite ices grown at 30 K. A set of porous H{sub 2}O:CH{sub 4} ices are taken as a prototypical example. As a benchmark and proof of concept, the stoichiometry of the ice constituents is retreived with good accuracy from the refractive indices and the extinction coefficients of the reference binary ice mixtures with known compositions. Accurate band strengths are then calculated from experimental mid-infrared spectra of complex ices. We notice that the presence of pores has only a small effect on the overall band strengths, whereas a water dilution can considerably alter them. Different levels of porosity are observed depending on the abundance of methane used as a gas contaminant premixed with water prior to background deposition. The absorption profiles are also found to vary with deposition rate. To explain this, we use Monte Carlo simulations and we observe that the deposition rate strongly affects the pore size distribution as well as the ice morphology through reorganization processes. Extrapolated to genuine interstellar ices, the methodology presented in this paper can be used to evaluate the porosity and to quantify the relative abundances from observational data.
ISSN 0004637X
Educational Use Research
Learning Resource Type Article
Publisher Date 2015-11-20
Publisher Place United States
Journal Astrophysical Journal
Volume Number 814
Issue Number 1


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