[in Japanese]

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[in Japanese]

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　We theoretically investigated physisorption on ice Ih and ice XI surfaces, because the physisorption states of adsorbates play important roles in the chemical reaction on the interstellar medium, which generally consists of ice, with the extremely low temperature (10 K) condition. In this paper, we focused on hydrogen molecules as adsorbates because hydrogen is the most abundant element in space. At first, we briefly reviewed the way to treat the van der Waals interaction in density functional theory. We also showed the calculated adsorption states of hydrogen molecules on ice Ih and ice XI surfaces. We found the non-local correlation functional, which can treat the dispersion interaction, improved the potential energies of physisorbed hydrogen molecules on ice Ih and ice XI surfaces.

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　Infrared spectroscopy combined with the matrix isolation method, where samples are trapped by a cold and inert-molecular solid, has been used for the investigations of small water clusters. After the descriptions of the stable structures and vibrations of the clusters, the author explains experimental techniques of the matrix isolation and demonstrates recent works on the clusters isolated in the solids of rare gases, para-hydrogen, and methane as well as the hydrogen adsorption layer on a vapor deposited NaCl film. The relation between the frequency shift of the hydrogen-bonded OH stretch and the matrix critical-temperature is also shown.

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　Chemistry of interstellar H₂O is essential for understanding the formation of stars and planetary systems because of the ubiquity of H₂O in space. The abundance ratio of nuclear spin isomers (the ortho-to-para ratio, OPR) can be a key for interstellar water chemistry, when assuming that the OPR desorbed from ice is closely related to the ice formation temperature. However, the above assumption has not been experimentally validated. Here, we report that H₂O photodesorbed from ice at 10 K shows a statistical OPR of 3, even when the ice is produced in situ by hydrogenation of O₂, a known formation process of interstellar H₂O. This invalidates the hypothesis for relation between OPR and temperature. Reinterpretation of previous observations is necessary to improve our understanding of interstellar chemistry and the formation of the solar system and comets.

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　Active oxygen species (AOS) generated via ultraviolet lamps can be applied for various industrial processes owing to extremely strong oxidative abilities. It is well known that excited singlet oxygen atom [O(¹D)], excited oxygen molecule (¹O₂), ozone (O₃) and hydroxyl radicals (OH*), are of interest and value in surface modification, cleaning and oxidation processes. We have been investigated a new sterilization method using the AOS, and it is important to evaluate damages of polymer devices due to the exposure of the AOS for using as a sterilization apparatus. In this paper, we evaluated degradation behaviors of polymers used for medical devices due to the exposure of the AOS by using a colorimeter, spectrometer and pull test apparatus. We found that these polymer characteristics as bulk materials were maintained, although those of the surfaces were deteriorated by the AOS exposure.

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