In polycrystalline ice

Fig. 9. Spectrum of energy losses in polycrystalline ice (taken from Ref. 85).

In order to demonstrate that Fast Thermal Desorption spectroscopy can be used successfully to study reactions in volatile polycrystalline materials and to gain insights into nanoscale molecular transport in polycrystalline ice, we have conducted preliminary studies of H/D exchange kinetics near ice melting point. Figure 7 illustrates our approach. 

Several experiments reviewed in this article illustrate just a small fraction of opportunities for research into the fundamental physical and chemical properties of ice offered by our experimental approach. We emphasize that our core method, i.e., the FTDS can be combined with a variety analytical techniques. For instance, the existing apparatus can be equipped with an FTIR spectrometer for better initial characterization of phase and chemical composition of ice films during deposition. At the present time we are also developing an optical system that would allow us to conduct studies of photochemical reactions in polycrystalline ice. While our USC measurements were conducted with a fixed heating rate, further improvement of this particular component of our apparatus will make... 

Photolysis in ice has a role also for inorganic compounds. As an example, it was found that the photoreductive dissolution of iron oxide particles to form bioavailable iron (Fe(II)aq) was slow in aqueous solution (pH 3.5) but was significantly accelerated in polycrystalline ice. This occurred independently on the irradiation wavelength and on the type of oxides [hematite. 

In Section V, the ESR studies on supercooled water confined in polycrystalline ice are presented in detail. Finally, conclusions of this review are summarized in Section VI. 

In polycrystalline ice liquid water is localized, like in a sponge, in the intergranular junctions (pockets) connected by vein systems [48,51,53-55] that serve as interstitial reservoirs for impurities [48,56]. The average volume of the pockets and volume per unit length of the veins are controlled by temperature and pressure, and independent of the average grain size [48,49]. The vein system has been impressively visualized by colloidal nanoparticles that are excluded from ice grains and form chains in the ice veins [55]. 

Mader, H. M. 1992a. Obsovations of the water-vein system in polycrystalline ice. J. Glaciol. 38, No. 130,333-347. 

Nye, J. F. 1992. Wato veins and lenses in polycrystalline ice. In Physics and Chemistry of Ice, edited by N. Maeno and T. Hondoh, Hokkaido University Press, 1992, SeqqxHO, pp. 200-20S. 

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