Ices of CO2/H2O Mixtures. Reflection-Absorption IR Spectroscopy and Theoretical Calculations

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• 作者：Belé ; n Maté ; Oscar G&aacute ; lvez ; Beatriz Martí ; n-Llorente ; Miguel A. Moreno ; Ví ; ctor J. Herrero ; Rafael Escribano ; Emilio Artacho
• 刊名：Journal of Physical Chemistry A
• 出版年：2008
• 出版时间：January 24, 2008
• 年：2008
• 卷：112
• 期：3
• 页码：457 - 465
• 全文大小：397K
• 年卷期：v.112,no.3(January 24, 2008)
• ISSN：1520-5215

文摘

Ice mixtures of CO<SUB>2 and H₂O are studied using Fourier transform reflection-absorption infrared (RAIR)spectroscopy. Mixtures are prepared by sequential deposition or co-deposition of the two components fromthe gas phase onto an Al plate kept at 87 K inside a low-pressure chamber. Two CO₂ structures are found inmost experiments: a crystalline form similar to pure CO₂, which evaporates when warming at 105 K, and anoncrystalline species which remains embedded in amorphous water ice after warming. Significant spectralvariations are found depending on the deposition method and the thickness of the solid. Features characteristicof the RAIR technique appear in the spectral regions of the normal modes of the bending and asymmetricstretching CO₂ vibrations. Simulations using Fresnel theory and Mie scattering are carried out with acceptableagreement with the experimental spectra of solids of variable thickness, from ~1 m to the limit ofnanoparticles. Theoretical calculations of a pure CO₂ crystal are performed. The relaxed geometry of thesolid and its vibrational spectrum are determined and compared to the experimental results.