RESUMO
The Raman spectra of binary solution (CCl4 and C6 H6) and pure liquid were measured up to pressures of 11 GPa. The results show that pressure effect on binary solution is different from that on pure liquid: When mixing two liquids, owing to the changes in the density of the solution, intermolecular distance decreases and interaction energy increases, the frequency shift (blue shift) of spectral bands increases, and the frequency shift of binary liquid is faster than pure liquid frequency shift. Phase transitions (spectral bands splitting) change earlier and natural frequency difference delta0 increases with increasing pressure, while the Fermi resonance bands nu1 + nu6 and nu8 of benzene and nu1 + nu4 and nu3 of CCl4 disappear as the pressure decreases gradually, the spectral bands with different compressibility have different speed, whereas CCl4 has smaller density, longer bond, smaller force constant and larger compressibility and is easy to compress, C6H6 has larger density, smaller bond, larger force constant, smaller compressibility and is hard to compress. The frequency shift of CCl4 is faster than benzene. In this paper we provide good reference on Raman bands assignment and certification under high pressure, and also provide methods and ideas for study of the different environment of high pressure effect, intermolecular interaction and solvent effect.
RESUMO
The Raman scattering coefficients of the fundamental v1 (992 cm(-1)) of C6 H6 and the fundamental v1 (656 cm(-1) ) of CS2 changed dramatically with relative concentration of the binary solution of CS2 and C6 H6. The Raman spectra of the binary solution with different relative concentrations were measured. The results show that both the v1 fundamentals intensities changed dramatically with the relative concentration of the solution and the fundamental v1 of C6 H6 has little effect on the Fermi resonance v1 +v6-v8. On the contrary, the change in the v1 fundamental intensity of the CS2 changed which has more effect not only on the Fermi resonance v1 - 2v2 but also on the v2 fundamental. In this report, the experimental results were analyzed based on the J. F. Bertran theory and group theory.
RESUMO
The binary systems of 1,1,3,3-tetramethylurea (TMU) with water, TMU with methanol, TMU with ethanol and N,N-dimethylformamide(DMF) with water were measured by Raman method. With the analysis of the frequency changes of stretching vibration of carboxyl with concentration the authors found that the frequency shift underwent two processes: first, the frequency of stretching vibration of carboxyl down shifts with the increase in hydrogen-bond acceptor concentration; secondly, when the concentration of binary system surpasses a critical value, the wave number remains almost constant, and only the rela tive intensity changes. Through this critical volume ratio, the authors found that the large self-associated water molecule was in volved in the TMU aqueous binary system; while the small self-associated molecule or dimer formation was present in other binary systems.
RESUMO
Lycopene and beta-carotene are two important nutritional components in tomato. The main Raman spectrum group of lycopene and beta-carotene abundant in tomato is identical and difficult to be distinguished through fundamental frequency. With excitation wavelength of 514.5 nm, the excited light was just present in the half width range of the main absorption bands of Lycopene and beta-carotene, so the resonance Raman effect can occur. Based on resonance Raman spectra, by on-body measuring the second harmonic of stretching vibration of carbon-carbon conjugated double bond in lycopene and beta-carotene, the content of lycopene and beta-carotene can be obtained according to the integrated intensity of each component calculated by software. And this provides a method for on-body determining the content of the components with the homologous group.
