PubMed · 3046427
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D L Gerrard, H J Bowley. 1988-06-15. Raman spectroscopy.. https://doi.org/10.1021/ac00163a023
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Recent theoretical and experimental studies of evaporation have suggested that on average, molecules in the higher-energy tail of the Boltzmann distribution are more readily transferred into the vapor during evaporation. To test these conclusions, the evaporative cooling rates of a droplet train of liquid water injected into vacuum have been studied via Raman thermometry. The resulting cooling rates are fit to an evaporative cooling model based on Knudsen's maximum rate of evaporation, in which we explicitly account for surface cooling. We have determined that the value of the evaporation coefficient (gamma(e)) of liquid water is 0.62 +/- 0.09, confirming that a rate-limiting barrier impedes the evaporation rate. Such insight will facilitate the formulation of a microscopic mechanism for the evaporation of liquid water.
A set of arabinoxylan samples differing in their arabinose composition and various samples of arabino-xylo-oligosaccharide samples were analysed by Raman spectroscopy. Specific signatures for arabinose substitution were found in several spectral regions, that is, 400-600, 800-950 and 1030-1100 cm(-1). A linear relationship was observed between the peak ratio 855/895 cm(-1) of the second derivative spectra and the A/X ratio determined by chemical analysis. Moreover, spectral changes were observed in the 400-600 cm(-1) region assigned to the coupled vibrations mode in the skeleton: while the intensity of the band at 570 cm(-1) increased with the degree of substitution, that at 494 cm(-1) decreased. Similarly, a linear relationship was observed between the peak intensity ratio 570/494 cm(-1) calculated on the second derivative spectra and the composition data. Analysis of Raman spectra of arabino-xylo-oligosaccharides allowed to identify specific spectral features of disubstitution.
A study of the vibrational behavior of five saturated monoacid triacylglycerides is performed by Raman spectroscopy at room temperature in the 3100-500 cm(-1) spectral range. The splitting of the CO stretching mode leads to conclude on the existence of two or three geometries of CO in the "knot" group OCO. The CO stretching mode seems to be a good tool for distinguishing the polymorphic forms of the studied triglycerides. The assignments of the different CH stretching modes are performed in the 1500-500 cm(-1) spectral range. The I(2845)/I(2880) (in the CH stretching spectral region) and I(1445)/I(1296) intensity ratios (between the maximal intensity I(1445) of the CH(2) scissoring mode and the maximal intensity I(1296) of the skeletal vibration of (CH(2))(n) in-phase twist) seem to depend on the type of polymorphic forms of these molecules.