Raman scattering experimental/theoretical spectra

The solvent-induced stereochemical behaviour of a bile acid-based biphenyl phosphite has been studied experimentally using circular dichroism (CD) spectroscopy, and theoretically using DFT quantum mechanical methods. " The FTIR, Raman and surface-enhanced Raman scattering (SERS) spectra of phenyl phosphate disodium salt have been recorded and its vibrational wavenumbers, calculated using the Hartree-Fock/6-31G basis set, compared with experimental values. From SERS spectra study, the molecule is adsorbed on the silver surface with the benzene ring in a tilted orientation. The presence of the phenyl ring and the phosphate group vibrations in the SERS spectrum reveal the interactions between the phenyl... 

Raman spectroscopy uses an incident laser beam that is focused on the sample. The intensity of the scattered light is measured as a function of its frequency. Bands appear in the spectrum that are shifted in frequency from the frequency of the incident light. Each shift in frequency corresponds to one of the vibrational frequencies of the molecule. Infrared spectroscopy measures the absorption of infrared light as a function of its frequency. Absorption bands appear in the spectrum that correspond to vibrational frequencies in the DNA. Infrared spectroscopy is hindered by the strong almost continuous absorption band of water while Raman spectroscopy benefits from the fact that water is a weak Raman scatterer. Infrared spectroscopy is of greater usefulness in the studies of films and fibers while Raman is of use in obtaining the vibrational frequencies of DNA in crystals, films, fibers, and aqueous solutions. A large amount of evidence, both theoretical and experimental, now exists which shows that there is a close relation between the conformation of a DNA and the frequencies and the intensities of certain bands in the Raman spectra. The theory for the relation between the frequencies and intensities and the DNA conformation is outlined in the next two sections. 

Figures 8 and 9 shows a part of the bending region at low temperature containing the components of Vg (150-160 cm ) and Vs (190-200 cm ). The Vg vibration, IR active in the free molecule, has weak components in the Raman spectrum. According to theoretically calculated Raman intensities, which almost perfectly fit the experimental spectrum, the big component has a very low scattering cross-section [87] and is accidentally degenerate with the b2g component at ca. 188 cm. The IR active components of Vg cause strong absorptions in the IR spectrum even if the crystalline sample used for transmission studies is as thin as 400 pm [107, 109].

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