Effect of molecular structure nonrigidity on anisotropy of dipole absorption cross section

The influence of the nonrigidity of free complex asymmetric top molecules on the anisotropy of the absorption cross section over various rotational configurations has been studied under conditions where the total angular momentum is conserved. It is shown that the nonrigidity-induced cross section anisotropy is maximal for the optical transition with the dipole moment collinear to the axis of the molecule’s mean moment of inertia and rapidly decreases with the rise of the intramolecular flexibility. For all types of tops, disturbances from internal motions are stronger in the region where the principal axes of inertia are collinear with the total rotational angular momentum.     

Effect of structure anisotropy on low temperature spin dynamics in quantum wells

Spin dynamics of two-dimensional electron gas confined in an asymmetrical quantum well is studied theoretically in the regime where the scattering frequency is comparable with the spin precession frequency due to the conduction band spin splitting. The spin polarization is shown to demonstrate quantum beats. If the spin splitting is determined by both bulk and structural asymmetry mechanisms the beats are damped at zero temperature even in the absence of a scattering. We calculate the decay of spin beats due to the thermal broadening of the electron distribution function and electron scattering. The magnetic field applied along the structure growth axis is shown to increase the frequency of the beats and shift system towards the collision dominated regime.     

Optical anisotropy of aligned pentacene molecules on a rubbed polymer corresponding to the electrical anisotropy

We report on the optical anisotropy of a pentacene film on a rubbed (poly)vinylalcohol (PVA) layer related to the electrical performances of the pentacene organic field effect transistors (OFETs) depending on the direction of a current flow. The optical anisotropies of the PVA films are negligible with respect to whether or not rubbing process. In the pentacene OFET on the rubbed PVA layer, however, the optical anisotropy is observed and the anisotropy of the electrical performances directly corresponds to the optical anisotropy of the pentacene thin-film on the rubbed PVA layer.     

Effect of energy transfer on the kinetics of the decay and anisotropy of luminescence of prodan molecules

The temporal characteristics of the decay and polarization of luminescence of prodan solutions with different concentrations, excited by a picosecond laser radiation, are studied. The kinetics of the emission decay and polarization depend on the spectral range of luminescence recording and on the luminophore concentration and reflect the relaxation processes (leading to a long-wavelength shift of the entire emission band) and, in the case of sufficiently high concentrations, nonradiative energy transfer between the prodan molecules. It was found that the evolution of luminescence anisotropy in a diluted solution depends on the recording wavelength, which allowed us to calculate the average times of the Brownian rotational diffusion for prodan in glycerol, whose maxima were determined to be about 40 ns in the spectral region near 520 nm and to decrease to 14 and 17 ns at the edges of the emission region at 450 and 560 nm, respectively.     

Influence of the structure of fullerene molecules on their clusterization in the crystalline matrix

The influence of the processes occurring during clusterization of fullerene molecules in solutions on their nonlinear optical properties has been considered. A new derivative of fullerene C₆₀, namely, monofulleropyrrolidine containing a specific group, which is known as sterically hindered phenol, has been analyzed using the previously proposed criteria, i.e., an empirical criterion, which is involved in the analysis of the emission spectrum of the frozen solution, and a theoretical criterion, which is based on the quantumchemical calculation. The performed experimental investigations of the frozen solution of this fullerene derivative in toluene completely confirmed the conclusions following from the results of theoretical calculations and demonstrated a low efficiency of the clusterization of fullerene molecules in this solution and, correspondingly, a low efficiency of its nonlinear optical response. It has been shown that quantum-chemical calculations can serve as the basis for prior testing of possible fullerene derivatives for the subsequent controllable chemical synthesis of a derivative with required properties.     

Effect of photonic crystal structure on the nonlinear optical anisotropy of birefringent porous silicon

Anisotropic photonic crystal structures consisting of birefringent porous silicon layers with alternating porosity were fabricated. The in-plane birefringence formed as a result of anisotropic etching in Si(110) results in unique multilayered structures with two distinct photonic bandgaps for orthogonal light polarizations. Nonlinear optical studies based on the third-harmonic generation from these structures demonstrate variation in the symmetry of the nonlinear optical response.     

Mathematical simulation of complex formation of protein molecules allowing for their domain structure

A physical model of the interactions between protein molecules has been presented and an analysis of their propensity to form complex biological complexes has been performed. The reactivities of proteins have been studied using electrostatics methods based on the example of the histone chaperone Nap1 and histones H2A and H2B. The capability of proteins to form stable biological complexes that allow for different segments of amino acid sequences has been analyzed. The ability of protein molecules to form compounds has been considered by calculating matrices of electrostatic potential energy of amino acid residues constituting the polypeptide chain. The method of block matrices has been used in the analysis of the ability of protein molecules to form complex biological compounds.     

Effect of pressure anisotropy on magnetorotational instability

It is shown that two new instabilities of hybrid type can occur in a rotating magnetized plasma with anisotropic pressure, i.e., the rotational firehose instability and the rotational mirror instability. In the case of β_∥ > β_⊥, where β_∥ and β_⊥ are the ratios of the parallel and perpendicular plasma pressure to the magnetic field pressure, the pressure anisotropy tends to suppress both new instabilities; in the case β_⊥ > β_∥, it leads to their strengthening. In the latter case, the perturbations considered can be unstable even if the Velikhov instability criterion is not satisfied. The text was submitted by the authors in English.     

Effect of local anisotropy on spin glass

The effects of uniaxial crystal field on spin glass properties are investigated. The parallel susceptibility (χ∥) exhibits sharper cusp than the perpendicular one (χ⊥).     

Polarizability of molecules on their vibrational excitation

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 53, No. 5, pp. 793–800, November, 1990.     

The structure of pure tertiary butanol

The technique of second-order difference neutron scattering with hydrogen/deuterium isotopic substitution has been used to measure the intermolecular structural correlations in pure liquid tertiary butanol. The newly developed technique of empirical potential structure refinement has been used to perform a detailed structural analysis of the resulting partial distribution functions, providing a means by which a full set of interatomic partial distribution functions consistent with the experimental data can be extracted. A comparison with our experimental results is made for a Monte Carlo model produced using fixed potentials as in earlier simulations of this alcohol system, and for the model which results from our procedure. The results suggest that the extent of intermolecular hydrogen bonding, although significant, is less dominant than generally accepted.     

Influence of anisotropy on the structure of an ion-sound wave

We study the influence of magnetic field on the ion-sound disturbance of a weakly ionized plasma ahead of a strong shock wave of the neutral component. Different regimes (subsonic, sonic, and supersonic) are studied. Main attention is paid to the case of formation of a discontinuous field in the plasma. Radiophysical Research Institute, St. Petersburg University, St. Petersburg, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 2, pp. 120–128, February 1999.     

Effect of crystal anisotropy on superconductivity in zinc

The effect of crystal anisotropy on superconductivity in zinc has been studied making use of the recently observed highly anisotropic vibrations of a zinc atom in its crystal. The effect of crystal anisotropy on superconductivity turns out to be quite involved and significant.     

Effect of anisotropy on acoustoelastic birefringence in wood

The ultrasonic velocity of shear waves propagating through radial direction of a wood plate specimen, transversely to the loading direction, was measured. By rotating an ultrasonic sensor, the oscillation direction of the shear waves was varied with respect to the wood plate axis and loading direction. The relationship between shear wave velocity and oscillation direction was examined to discuss the effect of anisotropy on the acoustoelastic birefringence in wood. The results obtained were summarized as follows. When the oscillation direction of the shear wave corresponded to the tangential direction of the wood specimen regardless of the stress direction, shear wave velocity decreased markedly and the relationship between shear wave velocity and rotation angle tended to become discontinuous. That is, when the shear waves oscillated in the anisotropic axis of the wood, the shear wave velocity peaked unlike in the case of oscillation in the stress direction. In an isotropic material (acrylic, aluminum 5052), on the contrary, when the shear waves oscillated in the stress direction of the specimen, the shear wave velocity peaked regardless of the main-axis direction of the specimen. On the basis of the discussion of these results, the ultrasonic shear wave propagating in wood under stress is confirmed to be polarized in the anisotropic axis of the wood.     

Effect of the lattice structure of nickel nanoparticles on their practical magnetization

Magnetization of nickel nanoparticles with various lattice structures is studied. Nickel particles with the fcc structure are shown to be magnetically harder than the particles with the icosahedron structure. Easy magnetization axes in the particles are found.