Raman structural study of ethylene glycol and 1,3-propylene glycol aqueous solutions.

Raman spectra of ethylene glycol (EG) and 1,3-propylene glycol (1,3-PG) aqueous solutions with the diol content from 10 to 90 mol% were measured. The diol content weakly influences the EG and 1,3-PG Raman bands in the spectra of the solutions in the region 250-1800 cm-1. This fact means that the conformational compositions of both the diols do not change significantly with dissolving in water. The intensity of the OH stretching band with respect to the diol bands intensities is the linear function of the ratio of the mole contents of water and the diol in the solutions. The spectral region 2800-3800 cm-1 can be used to evaluate the chemical composition of these binary solutions. DFT modeling of the Raman spectra of EG molecule in water shell confirms the prevalence of the gauche-conformation of EG in the aqueous solutions.

Relations between the Raman spectra and molecular structure of selected carotenoids: DFT study of α-carotene, ß-carotene, γ-carotene and lycopene.

Using the density functional theory (DFT), we calculated the structures and Raman spectra of trans-isomers of α-carotene, ß-carotene, γ-carotene and lycopene as well as trans-isomers of modified ß-carotene and lycopene molecules with substituted end or/and side groups. The DFT calculations showed that the position of the CC stretching band depends mainly on the number of conjugated CC bonds and decreases with an increase in the conjugation length. The weak dependence of the position of the CC stretching band on the structure of the carotenoid side and end groups suggests that this band can be used to evaluate the conjugation length for trans-isomers of various molecules containing polyene chains. The CC stretching band shifts towards lower wavenumbers with growth of the conjugation length or masses of the end groups and to higher wavenumbers in the presence of the side CH3 groups. The intensities of the CC and CC stretching bands are enhanced with growth of the conjugation length or masses of the end groups. The presence of the side CH3 groups results in bending of the carotenoid backbone, splitting and dumping of intensities of the CC and CC stretching bands.

DFT study of Raman spectra of polyenes and ß-carotene: Dependence on length of polyene chain and isomer type.

We carried out calculations of non-resonance Raman spectra of ß-carotene and polyenes CH2(CHCH)n-2CHCH2 using the density functional theory (DFT). We revealed that the peak positions and intensities of the CC and CC stretching bands depend on length of the polyene chain and type of the isomer. Our experimental non-resonance Raman spectra of ß-carotene powder match well the DFT-simulated Raman spectrum of ß-carotene in the all-trans form. The peak positions and relative intensities of the CC and CC stretching bands of ß-carotene turned out to be similar in the resonance and non-resonance Raman spectra. An increase in the number of conjugated double bonds (n = 3-30) in a polyene structure results in a monotonous shift of the positions of the most intense CC and CC bands towards lower wavenumbers with an increase in the band intensities. An increase in the isomer number results in the monotonous decrease of the CC stretching band intensity for polyenes with 9, 10, 11, 15 and 24 double bonds. An increase in the isomer number inhomogeneously influences the form, position and intensity of the CC stretching band.

Short-period multilayer X-ray mirrors.

Multilayer structures with short periods have been systematically investigated using a tunable soft X-ray synchrotron, BESSY II, and X-ray tube radiation. Multilayer X-ray mirrors of W/B(4)C, W/Sc, Mo/B(4)C, Mo/C, La/B(4)C, Cr/C and Cr/Sc, with periods from 0.8 nm to 3.5 nm and number of periods up to 300-400, were constructed and investigated. The high reflectivity and spectral resolution of the mirrors allow them to be used to create multimirror systems for X-ray diagnostics of high-temperature plasma, for X-ray astronomy and microscopy.