Spectral Characteristics of Subcritical Carbon Dioxide in Nanoporesстатья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:Coherent anti-Stokes Raman scattering spectra measured within the Q-branch of the vibrational transition v(1) are used to gain insights into the state of carbon dioxide molecules in nanopores of Vycor(TM) glass at room temperature (20.5 degrees C) and a subcritical temperature of 30.5 degrees C and gas pressures up to the saturation point P(sat) for each temperature. Along with the main spectral component, belonging to gaseous CO(2) molecules, the spectra recorded at pressures close to P(sat) feature a second (low-frequency) component. The second component is associated with the contribution from the CO(2) molecules trapped inside pores. A spectral deconvolution with account for the interference of these two bands makes it possible to estimate the spectral characteristics of the second (low-frequency) component at each temperature. At 20.5 degrees C, the bandwidth of the low-frequency component decreases with CO2 pressure, a behavior that can be explained by the transition of CO(2) from the adsorbed to the condensed state in the pore. At the subcritical temperature of 30.5 degrees C, the spectral width of the second component is pressure-independent and close to the value measured in the bulk of the supercritical fluid, a result likely associated with a low-temperature shift of the critical point of the substance trapped in nanopores.