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Интеллектуальная Система Тематического Исследования НАукометрических данных |
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Structure and transformation of molecular spectra at absorption and condensation in nanoporesтезисы доклада
- Авторы: Arakcheev V.G., Morozov V.B., Olenin A.N., Valeev A.A.
- Сборник: 8th European Conference on Nonlinear Spectroscopy and 28th European CARS Workshop, book of abstracts
- Тезисы
- Год издания: 2009
- Место издания: Advanced Physical Technologies and New Materials Department of Frascati ENEA Research Center Frascati, Rome, Italy
- Аннотация: Porous structures are widely used in various physical, chemical, and biological processes. This was shown in our recent works that carbon dioxide Raman spectral response in pores with diameter of several nanometers allows to distinguish partial contributions of gas phase, molecular layer, adsorbed from gas phase on the pores walls, condensed liquid-like phase, and to observe capillary condensation in pores as pressure draws to saturation value PSAT [1,2]. Phase behavior of a molecular fluid under nanoporous confinement substantially depends on the pores size, their topology and morphology and differs substantially from phase behavior in bulk volume. Then the quite reasonable question of observable spectral shape description depending on porosity parameters is solved in the presented paper. Spectra fittings were accomplished using the coherent sum of two Lorenzian profiles. Linewidth and centre frequency values measured in gaseous carbon dioxide in bulk were used as a substitute for high-frequency peak parameters. Low-frequency peak parameters were fitted as originating from molecules of the adsorbed and condensed fluid within a nanostructure. The diffusion process is presumed to be slow enough in order the molecule to stay within its phase the whole time of the scattering. Model porogram based on the measured one is used to take pore size distribution into account. The porogram is corrected to take the adsorbate layer thickness into account. Adsorption and condensation equations were used to model quantities of the both phases. The model spectra are in good agreement with the experimental results. The appearance of low-frequency peak at T=21oC was shown to be caused by gas adsorption and condensation to a dense liquid-like state inside nanopores at pressures lower than PSAT. The role of adsorption decreases and the role of condensation grows as the pressure approaches PSAT. The work is supported by Russian Foundation for Basic Research (07-02-01331)
- Добавил в систему: Аракчеев Владимир Генрихович