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Spectral structure of compressed gaseous and near-critical carbon dioxide in nanoporesтезисы доклада
- Авторы: Arakcheev V.G., Bagratashvili V.N., Dubyanskiy S.A., Morozov V.B., Olenin A.N., Popov V.K., Valeev A.A.
- Сборник: 7th European Conference of Nonlinear Optical Spectroscopy, Book of abstracts
- Тезисы
- Год издания: 2008
- Место издания: University of Innsbruck Igls, Austria
- Первая страница: ET21
- Последняя страница: ET21
- Аннотация: In present investigation we demonstrate CARS-spectroscopy approach for studying condensation effects in nanoporous structures1. CARS-spectra of carbon dioxide Fermi dyad 1/22 Q branches were collected in compressed gas filling nanoporous glass sample. The nanoporous glass sample with average diameter of pores ~4 nm and void-solid ratio ~30% was filled with carbon dioxide in high-pressure cell. Spectra transformation with gas pressure increase was investigated at room T=21oC and near critical T=30.5oC temperature values at pressure range [0.6÷1]•PSAT (where PSAT is bulk saturated vapour pressure). At pressure range below 0.8•PSAT at T=21oC as well as at T=30.5oC spectra of both Q branches were close to Lorenzian (Fig. 1, a). Spectra had the same line width and shift as those measured in bulk volume at the same conditions. Essential spectra asymmetry appeared at pressure values ~0.85•PSAT. At T=21oC it manifested itself in a step in the low-frequency spectra wing (Fig.1, b). With pressure increase up to value ~0.93•PSAT low-frequency step transformed into well pronounced second peak (Fig.1, c). Further pressure increase up to value PSAT leaded to some increase of low-frequency peak intensity in comparison with “gas” peak (Fig.1, d). At near-critical temperature T=30.5oC spectra measured in pressure range [0.85÷1]•PSAT were essentially asymmetric but did not demonstrate two visually distinguishable peaks. The appearance of low-frequency peak at T=21oC as well as spectra asymmetry at T=30.5oC was caused by gas condensation to a dense liquid-like state inside nanopores at pressures less than PSAT. At T=30.5oC density values of near-saturated gas and uncompressed liquid were essentially closer, that leaded to essentially smaller relative shift between two peaks and thus made them visually unresolved. Spectra fittings for both temperatures were fulfilled using line width and relative shift values measured in gaseous and uncompressed liquid carbon dioxide in bulk. Spectra fits are in good agreement with measured spectra (Fig. 1 b, c, d). The work is supported by Russian Foundation for Basic Research 07-02-01331. 1. NJ Wilkinson, MA Alam, JM Clayton, R Evans, HM Fretwell, SG Usmar. Phys.Rev.Let., 69(24):3535, 1992
- Добавил в систему: Аракчеев Владимир Генрихович