Novel approaches in spectroscopy of interparticle interactions. Raman line profiles and dynamics in liquids and glasses

A novel fitting method implemented recently in vibrational spectroscopy of disordered systems is briefly overviewed. It enables modelling of real line profiles intermediate between Lorentzian and Gaussian by an analytical function which has an analytical counterpart in the time domain. Numerous applications of this theoretical approach are discussed.     

On the analytical solution of the Ornstein-Zernike equation with Yukawa closure

We discuss the solution of the Ornstein-Zernike equation for most general closure consisting of a sum ofM Yukawa-type exponentials. A formal solution for the factored case is bound for an arbitrary mixture of hard spheres introducing a general scaling matrix of dimensions M×M. A sufficient number of equations for this matrix is obtained from symmetry considerations and the boundary condition. We discuss also restricted and semirestricted case, for which explicit solutions in terms of the scaling parameters and input parameters are found.     

The Packing Coefficient of Liquid 2-Phenylnaphthalene Molecules at 396 K

A method of measuring the angular intensity distribution of monochromatic MoK f radiation, u = 0.71069 Å scattered by a thin layer of liquid 2-phenylnaphthalene C 10 H 7 -C 6 H 5 is proposed and results of such an experiment are presented. Fourier analysis of this distribution by the procedure of Warren-Krutter-Morningstar yielded electron-density radial-distribution function (EDRDF). The curve of radiation intensity was analysed by the pair functions method. The determined mean, mutual distances between molecules of liquid studied are: [rbar] 1 = 5.30 Å, [rbar] 2 = 7.43 Å, [rbar] 3 = 12.35 Å. X-ray structural analysis was applied to determine the packing coefficient of 2-phenylnaphthalene molecules at 396 K. From the known volume of the first coordination sphere as well as the specific volume of the molecule V 0 and taking into regard the structural model of intermolecular interactions, the most probable value of the packing coefficient of the molecules was found to be [kbar] = 0.64. This value falls in the range of [kbar] values permissible for liquid phase. The results concern a wide class of molecular liquids, in particular polar compounds being naphthalene derivatives.     

Determination of synthetic musk in ground water by liquid-liquid extraction-gas chromatography mass spectrometryEI北大核心CSCD

A gas chromatography-mass spectrometry GC-MS method was established to determine three different synthetic musksSMsfrom ground water. Dichloromethane as the extracting solventthe concentrated extracts were tested by GC-MS using the external standard quantitative method. Each sample was extracted three times with 40 mL dichloromethane respectively. The linearity test was carried out in the range of 20.0 to 2000 μµg/L the relative standard deviationRSDRRFof average relative response factor was less than 8.7%and the limits of detectionLODswere in the range of 0.007 to 0.012 μµg/L. The recoveries of three spiked ground water samples were all between 98.1% and 117.0%and the relative standard deviations were less than 13%. Musk xylene in the ground water sample was 0.013 μµg/Land the spiked real sample had the recoveries higher than 80%. This method was suitable for the detection of trace SMs in ground water. © 2022, Youke Publishing Co.,Ltd. All rights reserved.     

Optical constants and integrated intensities of liquid hexafluorobenzene between 4000 and 250 cm at 25 °C

The optical constants (real and imaginary refractive indices) of hexafluorobenzene were determined at 25 °C via transmission measurements. Experimental absorbance spectra measured on a Nicolet Impact 410 FTIR were converted to imaginary refractive indices using methods described in the literature. The real refractive indices were obtained by Kramers–Kronig transformation of the imaginary refractive indices. From the complex refractive indices, the molar absorption coefficient (E_m) and complex molar polarizability spectra were calculated. The integrated intensities for the E_1u fundamentals were obtained from the areas under the bands in the spectrum. These integrated intensities are compared to those for benzene and benzene-d₆ in the literature.     

A chiral axial next nearest neighbour xy-model for antiferroelectric liquid crystals

We describe a chiral axial next nearest neighbour xy-model to account for the various subphases exhibited by antiferroelectric liquid crystals made of chiral rod-like molecules. The assumed form of the interlayer interactions is based on physical processes which are discussed. Using a discrete model, the predicted sequence of transitions is SmA-SmC-SmC-FI_H-FI_I-FI_L-SmC ^* A, where FI stands for a ferriphase, as seen in many compounds. The ferri and SmC phases are characterized by relatively large angles between the c-vectors of successive layers and occur only when the compounds have high optical purity. The calculated field induced structures exhibit a plateau of the apparent tilt angle at , where is the tilt angle of the molecules in the ferriphase. The conoscopic figures in the presence of a field and ellipsometric parameters in the absence of a field have also been generated, which agree extremely well with the experimental results. Recent anomalous X-ray scattering studies prove the xy-character of the configurations, though the commensurate structures that are found in the ferriphase require an extension of the model to include lock-in terms. Received 23 August 1999     

Water droplets in a spherically confined nematic solvent: A numerical investigation

Recently, it was observed that water droplets suspended in a nematic liquid crystal form linear chains [Poulin et al., Science 275, 1770 (1997)]. The chaining occurs, e.g., in a large nematic drop with homeotropic boundary conditions at all the surfaces. Between each pair of water droplets a point defect in the liquid crystalline order was found in accordance with topological constraints. This point defect causes a repulsion between the water droplets. In our numerical investigation we limit ourselves to a chain of two droplets. For such a complex geometry we use the method of finite elements to minimize the Frank free energy. We confirm an experimental observation that the distance d of the point defect from the surface of a water droplet scales with the radius r of the droplet like .When the water droplets are moved apart, we find that the point defect does not stay in the middle between the droplets, but rather forms a dipole with one of them. This confirms a theoretical model for the chaining. Analogies to a second order phase transition are drawn. We also find the dipole when one water droplet is suspended in a bipolar nematic drop with two boojums, i.e., surface defects at the outer boundary. Finally, we present a configuration where two droplets repel each other without a defect between them. Received 11 December 1998     

Colloidal interactions in two-dimensional nematics

The interaction between two disks immersed in a 2D nematic is investigated i) analytically using the tensor order parameter formalism for the nematic configuration around isolated disks and ii) numerically using finite-element methods with adaptive meshing to minimize the corresponding Landau-de Gennes free energy. For strong homeotropic anchoring, each disk generates a pair of defects with one-half topological charge responsible for the 2D quadrupolar interaction between the disks at large distances. At short distance, the position of the defects may change, leading to unexpected complex interactions with the quadrupolar repulsive interactions becoming attractive. This short-range attraction in all directions is still anisotropic. As the distance between the disks decreases, their preferred relative orientation with respect to the far-field nematic director changes from oblique to perpendicular. Received 1 October 2002 and Received in final form 12 November 2002 RID="a" ID="a"e-mail: miko@cii.fc.ul.pt     

Influence of Intra-Molecular Conformational Transitions and some Physico-Chemical Quantities of Liquids on their Thermal Conductivity

It is shown that the thermal conductivity of various liquids can be described adequately by taking into account the influence of intra-molecular conformational transitions on the number of bimolecular collisions in the liquid phase. The proposed equations allow the calculation of this transport property at different temperatures.     

Use of chiral amino acid ester‐based ionic liquids as chiral selectors in CE

In this study, the applicability of a chiral ionic liquid (CIL) as the sole chiral selector in CE was investigated for the first time. In particular, five amino acid ester‐based CILs were synthesized and used as additives in the BGE in order to evaluate their chiral recognition ability. The performance of these CILs as the sole chiral selectors was evaluated by using 1,1′‐binaphthyl‐2,2‐diylhydrogenphosphate (BNP) as the analyte and by comparing the resolution values. Different parameters were examined, such as the alkyl group bulkiness and the configuration of the cation, the anion type of the CIL and its concentration, and the pH of the BGE, in order to optimize the separation of the enantiomers and to demonstrate the effect that each parameter has on the chiral‐recognition ability of the CIL. Baseline separation of BNP within 13 min was achieved by using a BGE of 100 mM Tris/10 mM sodium tetraboratedecahydrate (pH 8) and a chiral selector of 60 mM l ‐alanine tert butyl ester lactate. The run‐to‐run and batch‐to‐batch reproducibilities were also evaluated by computing the %RSD values of the EOF and the two enantiomer peaks. In both cases, very good reproducibilities were observed, since all %RSD values were below 1%.