IR spectroscopic study of surface properties of amorphous water ice |
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Authors: | A V Rudakova M S Poretskiy I L Marinov and A A Tsyganenko |
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Institution: | 1.Fock Institute of Physics,St. Petersburg State University,Peterhof,Russia |
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Abstract: | The state of the surface of amorphous ice with a specific surface area of about 160 m2/g obtained by the condensation of water vapor at 77 K is studied by IR spectroscopy. As the temperature increases to 130–160
K, absorption bands of surface hydroxyl groups vanish, whereas changes in bands characteristic of hydroxyl groups in the bulk
of ice are indicative of a phase transition of ice from amorphous to the polycrystalline structure. The surface sites of amorphous
ice are characterized with low-temperature adsorption of carbon monoxide. It is shown that there are two types of CO adsorption
sites, free hydroxyl groups and oxygen atoms of surface coordinately unsaturated water molecules. Upon adsorption of nitrogen,
methane, and carbon monoxide, in addition to the perturbation of surface OH groups, reversible changes in the spectrum are
observed in the region of vibrations of bulk hydroxyls, which indicate that the strength of hydrogen bonds between water molecules
in the surface layer of icy particles increases approaching the strength of these bonds in the crystal and that the ice surface
becomes less amorphous. These results indicate that the properties of the ice surface layer substantially depend on the presence
of adsorbed molecules. |
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