13C NMR study of polarizations and polarization ranges of vinylene groups in seven series of related compounds

Polarizations, polarization ranges and ratios of polarization ranges for vinylene groups in seven series, namely chalcone derivatives, ferrocene analogues of chalcone, stilbene derivatives, ferrocene analogues of stilbene, and styrene derivatives, were studied. The polarization ranges spanning the intervals between ¹³C NMR chemical shifts of the derivatives substituted by p-NO₂ and p-NMe₂ groups are compared in these related compounds. The influence of the side-chain groups in the vinylene moiety and of the sign of the polarization on the substituent-effect are discussed.     

Polarization transfer in then 2 P-excitation of alkali atoms by longitudinally polarized electrons

In (ns — np)-excitation of alkali atoms by polarized electrons some of the spin orientation of the primary electron beam is transfered to the excited atoms because of exchange collisions. In the present work the polarization transfer to Na, K, Rb, and Cs respectively is studied by looking for the circular light polarization of (np — ns)-decay radiation emitted in forward direction following impact excitation by a beam of longitudinally polarized electrons. Maximum polarization transfers are observed at collision energies with values about 1.5 times that ofnp-thresholds. The transfer increases with increasing atomic number. In case of (6s — 6p)-excitation of cesium 45% of primary electron spin polarization is transfered to the atoms at maximum. The agreement with available close coupling data is satisfactory.     

Response function theory of time-resolved CARS and CSRS of rotating molecules in liquids under general polarization conditions

A theoretical treatment of time-resolved CARS and CSRS is given that includes molecular rotation during the time interval between the excitation and probing light pulses. A molecular response function tensor is found that accounts for the vibrational relaxation and the rotational diffusion of the molecules. The ensemble average of this response function with an arbitrary set of polarization conditions for the light pulses yields a sum of three terms. Each term is the product of a polarization factor P_l and a molecular rotational relaxation function M_l. New polarization conditions are proposed that permit to measure each of these three terms separately.     

Ferroelectric properties of smectic C liquid crystals with induced helical structure

Ferroelectricity has been observed in liquid crystalline mixtures of chiral smectic C type with a helical structure induced by chiral guest molecules (pitch p ≈ 100 μm). Samples of thickness d?p form monodomains with finite zero-field electric polarization because the spontaneous polarization of the smectic layers is not compensated by the helical twist. The temperature dependence of the spontaneous polarization has been studied near the phase transition smectic C→ smectic A.     

Calculation of polarization energies in some III–VII and IV–VI compounds with stereochemically active (ns)2-ions

The polarization energies of AB compounds, with A a monovalent or divalent cation with an (ns)²-lone pair and B an anion with a noble gas electronic configuration, have been calculated to investigate whether the stereochemical activity of the (ns)²-ion can be understood in an ionic picture. Computations have been performed applying the computer program EWALD. Formal ionic charges and partly estimated polarizabilities have been used. The polarization energy is shown to be predominantly due to cation polarization and may constitute an appreciable fraction of the total lattice energy. Hence, it can play a crucial role in the formation of structures, in which the (ns)²-ion is in a noncentrosymmetrical environment.     

Polarization effect in the electronically excited state of benzene derivatives and related compounds

The energies of intramolecular charge-transfer bands and excited singlet and triplet states, as well as the molar absorption coefficients of mono- and para-disubstituted benzenes and monosubstituted naphthalenes and pyridines depend not only on the inductive and resonance substituent effects, but also on their polarization effect which can be characterized by σ_α constants. The polarization effect determines the lifetime of the triplet state and phosphorescence quantum yield of monosubstituted naphthalenes.     

Spin polarization of electrons elastically scattered from argon atoms in the Ramsauer-Townsend region

Spin polarization of elastic electron scattering from argon atoms in the Ramsauer-Townsend region (0.1–0.6 eV) is calculated using a relativistic method. Via the energy-angle dependent surfaces, the differential cross section and the spin polarization parametersS, T andU are presented as functions of both the electron energy and the scattering angle. It is shown that the spin polarization effect is significant along a projected curve in the energy-angle plane.     

Polarization and collision velocity dependence of associative ionization in cold Na(3p)-Na(3p) collisions

We studied the polarization dependence of the associative ionization (AI) process Na(3p) + Na(3p) → Na ₂ ⁺ at collision velocities between 100 and 700 m/s (5 and 200 K), using linearly and circularly polarized light for the excitation. We found that the polarization dependence varies strongly in the collision velocity range under study. At the high end of our scale preparation of both collision partners in the |m _j |=1/2 substates yields the highest AI-rate, but at low velocities this ceases being so: the polarization dependence becomes less pronounced and at the low end of our scale the preparation |m _j 2|, |m _j 2|=3/2, 1/2 is most effective. All cross sections increase strongly at lower velocities. Combined with previous work this maps the detailed polarization dependence from 100–2400 m/s (5-2500 K). From these total results it is concluded that at collision velocities ≧500 m/s mainly one molecular potential curve leads to AI, but that this changes considerably at lower collision velocities. The findings are compared with recent theoretical results by Geltman, and we find large discrepancies.     

Spin polarization and cross sections of electrons elastically scattered from heavy alkaline-earth atoms

Semi-relativistic approach is employed to compute the differential and integrated cross sections, spin polarizationP and the spin polarization parametersT andU for the scattering of electrons from barium and strontium atoms in the energy range from 2.0–300 eV. The projectile-target interaction is represented both by real and complex optical potential in the solution of Dirac equation for the scattered electrons. The real optical potential includes the static, a parameter free correlation polarization and a modified semi classical exchange potentials. The complex optical potential is constructed by adding a model absorption potential as its imaginary part to the real optical potential.     

A role of the hyperfine interaction of the negative muon and an electron shell in formingP-odd correlations in the muonic ion μ20 Ne

The weak interaction of neutral currents of the negative muon and nucleons results in arisingP-odd correlations in the radiative 2s→ 1s muon-ion transition. At the present paper we consider how the hyperfine muon-electron interaction influences forming these correlations in the muonic ion μ²⁰ Ne with oneK-electron. It is shown that the general form of expressions describing aP-odd asymmetry of an angular distribution of the quanta and their circular polarization does not depend on electron configurations. On the other hand such dependence takes place for expressions describing an angular correlation between the momenta of the quantum and the hard electron emitted in the μ-decay process at the 1s-orbit. Therefore we think that measuring theP-odd asymmetry of the angular distribution is the preferable experiment for studying the neutral currents interaction. The spin polarization of the muon at the 2s-orbit can be obtained by measuring the circular polarization of the quanta in the same experiment.     

Electrochemical investigation of corrosion and corrosion inhibition of iron in hydrochloric acid solutions

The inhibition effect of 1-methyl pyrazole (MPA) on the acidic corrosion of iron in 1.0 M HCl was studied at different concentrations (10^?3–10^?2 M) by potentiodynamic polarization and electrochemical impedance spectroscopy, and EIS measurements. It is found from the polarization studies that methyl pyrazole (MPA) behaves mainly as anodic inhibitor in HCl. Values of polarization resistance (R_p) and double layer capacitance (C_dl) in the absence and presence of MPA in 1.0 M HCl are determined. The adsorption of MPA on iron surface from HCl is found to obey Temkin adsorption isotherm.     

Cross sections and spin polarizations of electrons elastically scattered from oriented molecules (CH3I)

Elastic differential cross sections and spin polarizations for electrons elastically scattered from CH₃I are calculated using the independent atom model. Three molecular orientations with respect to the incident electron wavevector are considered — first, the molecule is oriented randomly, second, the electron wave front and molecular bond are parallel, and third, the wavefront and the bond axis are perpendicular. It will be seen to what extent orientational averaging weakens features of the cross section and spin polarization. The calculations show that cross section and spin polarization measurements are a possible tool for determining the degree of molecular orientation. There is no degeneracy betweenI–C andC–I in cross section and spin polarization measurements. The results presented here for 200 eV and 600 eV electrons scattered by CH₃I should be considered as a case study and it should be possible to find molecules and electron energies for which even more dramatic differences between the various orientations between the molecules and the electrons can be expected.     

Computer simulation of active layers in the electric double layer supercapacitor: Optimization of active layer charging modes and structure,calculation of overall characteristics

The structure and functioning modes of active layers in an electric double layer capacitor (EDLC) with an aqueous electrolyte are simulated by means of a computer. A model of active layers prepared from activated carbon materials is proposed, percolation estimates are performed and effective ionic conductivities are calculated. The polarization of active layers includes a sequence of two charging processes: first, galvanostatic and then potentiostatic. The proposed program of calculations involves mutual matching and optimization of seven parameters characterizing the active layer and conditions of charging processes. According to calculations, galvanostatic polarization of wide pores in the EDLC biporous active layer up to the limiting potential followed by potentiostatic polarization of fine pores allows the capacity C _sp = 246 F/g and the energy W _sp = 107 kJ/kg to be obtained in fractions of second.     

Spin polarization of Auger- and of photoelectrons from barium atoms exposed to circularly polarized radiation and their cross comparison

New results of spin polarization of both photoelectrons and Auger electrons are reported after 5p photoionization of free Ba atoms with circularly polarized light. A substantial polarization transfer from the spin polarized photons to the spin polarized photoelectrons and via the hole state orientation to the spin polarized Auger-electrons is observed. The cross comparison of the results for photoelectrons and Auger-electrons allows a quantitative test of the assumed two step model where both electron-emission processes occur in sequence.     

Strong enhancement of transient magnetic fields in Gd over Fe for oxygen ions at high velocities

Precision data on transient magnetic fields (TF) in ferromagnetic Gd and Fe were obtained for oxygen ions at velocities between 2 and 8v ₀ (v ₀=c/137) using the¹⁶O(3^?) state as probe. At the high velocities the TF in Gd were found to be twice as large as in Fe which is in contrast to the generally observed scaling with the polarization density of the hosts. Degrees of polarization could be deduced from TF strengths using measured ion fractions of singly occupiedK-shell. The values derived were compared with theoretical estimates based on spin exchange scattering as a possible polarization mechanism.     

Phase equilibrium in binary liquid-crystal mixtures of 4-n-pentyl-4′-cyanobiphenyl and phenyl benzoates

Differential scanning calorimetry and polarization microscopy were used to study the phase diagram of a mixture of nematic liquid crystals, 4-n-pentyl-4′-cyanobiphenyl and 4-n-octyloxyphenyl-4′-hexylbenzoate.     

Chemically induced dynamic electron polarization. The isotropic g-factor differences and the CIDEP of radicals produced by pulse radiolysis

Time resolved electron paramagnetic resonance spectroscopy was used to examine the electron spin polarization in the ·CH₂OH radical. The observation of the CIDEP dependence on the isotropic g-factor differences of the radical pair components leads to the conclusion that the S-T_o mixing of the electron-nuclear states in radical pairs is a dominant polarization pathway.     

Resonance anomalous surface X-ray scattering

Resonance anomalous surface X-ray scattering (RASXS) technique was applied to electrochemical interface studies. It was used to determine the chemical states of electrochemically formed anodic oxide monolayers on platinum surface. It is shown that RASXS exhibits strong polarization dependence when the surface is significantly modified. The polarization dependence is demonstrated for three examples; anodic oxide formation, sulfate adsorption, and CO adsorption on platinum surfaces. σ- and π-polarization RASXS data were simulated with the latest version of ab initio multiple-scattering calculations (FEFF8.2). Elementary theoretical considerations are also presented for the origin of the polarization dependence in RASXS.