POROSITY AND BAND-STRENGTH MEASUREMENTS OF MULTI-PHASE COMPOSITE ICES

Autor(es)

Bossa, Jean-Baptiste ^[1] ; Mate, Belen ^[2] ; Fransen, Coen ^[1] ; Cazaux, Stephanie ^{[1, 3]} ; Pilling, Sergio ^[4] ; Monteiro Rocha, Will Robson ^[4] ; Ortigoso, Juan ^[2] ; Linnartz, Harold ^[1]

Afiliação do(s) autor(es)

^[1] Leiden Univ, Leiden Observ, Sackler Lab Astrophys, NL-2300 RA Leiden - Netherlands

^[2] IEM CSIC, Inst Estruct Mat, E-28006 Madrid - Spain

^[3] Kapteyn Astron Inst, NL-9700 AV Groningen - Netherlands

^[4] Univ Vale Paraiba, Inst Pesquisa & Desenvolvimento, BR-12244000 Sao Jose Dos Campos, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: ASTROPHYSICAL JOURNAL; v. 814, n. 1 NOV 20 2015.
• Citações Web of Science: 10

Resumo

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 H2O:CH4 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. (AU)

• Processo FAPESP: 09/18304-0 - Síntese e degradação de espécies moleculares pré-bióticas em atmosferas planetárias, cometas e gelos interestelares simulados
• Beneficiário: Sergio Pilling Guapyassu de Oliveira
• Linha de fomento: Auxílio à Pesquisa - Apoio a Jovens Pesquisadores
• Processo FAPESP: 13/07657-5 - Modelagem computacional do ambiente circum-estelar de protoestrelas empregando dados de gelos bombardeados por raios cósmicos simulados em laboratório
• Beneficiário: Will Robson Monteiro Rocha
• Linha de fomento: Bolsas no Brasil - Doutorado