Polarized infrared spectra: Part 1. Stretched polymer method. Fundamental vibrations of some mono- and di-substituted benzenes

Polarized IR spectra of five benzene derivatives (four of C_2v symmetry and one of D_2h symmetry) have been recorded using the stretched polymer method. It has been found that the values of the dichroic ratios depend systematically on the symmetry class of the vibration in question. The IR-active vibrations can thus be unambiguously divided into the correct symmetry classes. The general validity of the method, as well as its value for vibrational analysis, is discussed.     

Analysis of superconductor oxides YBa2Cu3O8−x by inductively coupled plasma atomic emission spectrometry and complexometric titration

The elemental composition of superconductor oxides YBa₂Cu₃O_8−x were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) and complexometric titration. Samples were dissolved in dilute HCl. A sequential PU 7000 Philips inductively coupled plasma atomic emission spectrometer was used for the measurements. A comparison of the different atom and ion emission lines of yttrium, barium and copper was carried out. The effect of changes of forward radio frequency (RF) power coupled into the plasma on emission intensity of various spectral lines was studied. The RF power was changed from 0.8 to 1.2 kW. The changes in the net intensities (%) of the emission lines of Cu(I) at 324.754 nm, Cu(II) at 224.700 nm, Ba(II) at 455.403, Ba(II) at 493.409 nm, Y(II) at 371.030 nm and Y(II) at 360.073 nm were calculated. The indicator 1-(2-Pyridylazo)-2-Naphthol (PAN) and different buffers were used for the complexometric titration of Cu, Y and Ba. No statistically significant differences were found between the results of ICP-AES and chemical methods of analysis.     

Stability of crown-ether complexes with alkali-metal ions in ionic liquid-water mixed solvents

Stability constants of sodium and cesium ion complexes with 18-crown-6 (18C6) and dibenzo-18-crown-6 (DB18C6) in N-butyl-4-methyl-pyridinium tetrafluoroborate [BMP][BF₄] aqueous solutions were measured using the ²³Na and ¹³³Cs NMR technique at 23 °C. To the best of our knowledge, the estimated values of stability constants reported in this study are the first such values given for ionic liquid solutions. The cationic exchange between the free and complexed species is rapid, and only formation of the 1:1 complexes [M(18C6)]⁺ and [M(DB18C6)]⁺ (M = Na⁺, Cs⁺) were observed. The complex formation constants demonstrated a strong dependence on the [BMP][BF₄] concentration. For [M(18C6)]⁺, in solutions with a 0.33–0.70 mole fraction of water in [BMP][BF₄], lg K values are found to be more than one unit higher than the lg K values measured in pure aqueous solutions, although no information concerning the influence of [BMP][BF₄] on the complex formation selectivity could be observed. DB18C6 complexes revealed significantly lower stability under the same conditions. An extrapolation to zero water content gave the lg K = 2.42 for [Cs(18C6)]⁺ in [BMP][BF₄]. It was discovered that when added to water, [BMP][BF₄] increases the solubility of crown ethers and decreases the solubility of alkali metal nitrates. Complex formation with crown ethers enhances the solubility of alkali metal salts in [BMP][BF₄].     

Screening for vanadium in urine and blood serum by electrothermal atomic absorption spectrometry and D.C. plasma atomic emission spectrometry

Practical detection limits were 2 and 10 μg l^?1 vanadium for pyrolyte graphite-furnace a.a.s. and d.c.p.-a.e.s., respectively, which allowed screening for urinary vanadium (? 10 μg ?in ? subjects, by direct measurements. Extraction of vanadium with ammonium 1?inecarbodithioate into 4-methylpentan-2-one gave detection limits of 0.5 and ? μg l^?1 vanadium, respectively, for the two techniques.     

Dispersion Theory of Liquids Containing Optically Linear and Nonlinear Maxwell Garnett Nanoparticles

Kramers-Kronig relations and sum rules for effective linear permittivity of the Maxwell Garnett liquid-nanosphere system were obtained using complex analysis and general expression of the effective permittivity. When reflectance from optically linear and nonlinear Maxwell Garnett nanoparticles was calculated it was observed that the reflectance, in the case of attenuated total reflection, depends on the fill fraction of the nanospheres and their nonlinear susceptibility. According to simulations a good sensitivity of the nonlinear contribution on the reflectance can be obtained by using a probe wavelength corresponding to the resonance frequency of the nanosphere system. In Kretchmann#x0027;s configuration it was observed that the surface-plasmon-resonance angle depends on the fill fraction and on the intensity of the incident light. By using reflectance, it is possible to detect optically nonlinear nanospheres in liquids.     

Thermodynamics of cesium complexes formation with 18-crown-6 in ionic liquids

Thermodynamic data for cesium complexes formation with 18-crown-6 (18C6, L) [Cs(18C6)]⁺ in N-butyl-4-methyl-pyridinium tetrafluoroborate ([BMPy][BF₄], I), in 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF₄], II) and in 1-butyl-3-methylimidazolium dicyanamide ([BMIM][N(CN)₂], III) were measured with NMR ¹³³Cs technique at 23–50 °C. The stability of cesium complex in RTILs is estimated to be in the range between water and DMFA. Stability constants for [Cs(18C6)]⁺ are found to decrease as temperature is increasing. The following values for lgK(Cs+L) and ΔH(Cs+L) at 23 °C are determined: 2.6 (0.3), ?47(1) kJ/mol (RTIL I); 2.8(0.3), ?80(3) kJ/mol (RTIL II) and 3.03 (0.08), ?47(2) kJ/mol (RTIL III). It is demonstrated that enthalpy change promotes complex formation while the corresponding change of entropy is negative and provides decomposition of [Cs(18C6)]⁺.     

Communication modes in vector diffraction

The communication modes, which mathematically correspond to singular value decomposition, have proven a useful concept in optical scalar-field diffraction, with applications in resolution studies, image synthesis, and wave propagation. For optical near-field geometries the communication modes have to be extended to electromagnetic field accounting for the polarization properties. In this paper we present the vector-valued communication modes method based on the rigorous electric-field diffraction integral. As a special case the transverse-electric scalar field modes are obtained. The intensity and polarization properties of the leading electromagnetic communication modes in near-field arrangements with rectangular apertures are discussed in terms of the Stokes parameters. For small separations between the transmitting and receiving apertures the fundamental mode possesses a ring-shaped hollow structure. The polarization properties of the near-field modes show features on spatial scales smaller than the wavelength of light. The system symmetries lead to degenerate communication modes.