Vol 107, No 11 (2018)

The D(³He, p)⁴He reaction is first investigated in a solid target of deuterated zirconium (ZrD) in the ³He⁺ ion energy range E_He = 18–30 (E = 7.2−12.0keV keV in the center-of-mass system) with a step of 2 keV. The electron screening potential U_e = (617.8 ± 154.7) eV and the D(³He, p)⁴He reaction enhancement factors are experimentally determined in the given energy range. The measured electron screening potential is six times higher than in gaseous targets. This can be due to the ZrD lattice effects, which have not been studied either theoretically or experimentally so far. The D(³He, p)⁴He reaction has been investigated at the pulsed plasma Hall accelerator (Tomsk).

A novel fully self-consistent microscopic approach based on the energy density functional method is employed to calculate the fine structure of the pygmy dipole resonance in ²⁰⁸Pb, i.e., the energies and reduced probabilities of E1 transitions for the states with energies below 10 MeV. The approach includes the random-phase approximation, quasiparticle–phonon interaction and the single-particle continuum. The theoretical results are compared to the available high-resolution data and found to agree with measured integral characteristics of the pygmy dipole resonance at energies above 5.7 MeV. Residual spin–spin forces are quantified, and their contribution is found to be significant at both low and high energies. A recently proposed criterion is employed to analyze the collectivity of the 1^–states in ²⁰⁸Pb.

A microscopic model of the lipid membrane is constructed that provides analytically tractable description of the physical mechanism of the first order liquid–gel phase transition. We demonstrate that liquid–gel phase transition is cooperative effect of the three major interactions: inter-lipid van der Waals attraction, steric repulsion and hydrophobic tension. The model explicitly shows that temperature-dependent inter-lipid steric repulsion switches the system from liquid to gel phase when the temperature decreases. The switching manifests itself in the increase in lateral compressibility of the lipids as the temperature decreases, making phase with smaller area more preferable below the transition temperature. The model gives qualitatively correct picture of abrupt change at transition temperature of the area per lipid, membrane thickness and volume per hydrocarbon group in the lipid chains. The calculated dependence of phase transition temperature on lipid chain length is in quantitative agreement with experimental data. Steric repulsion between the lipid molecules is shown to be the only driver of the phase transition, as van der Waals attraction and hydrophobic tension are weakly temperature dependent.

We provide a very brief review of the description of colored invariants for the Hopf link in terms of characters, which need to be taken at a peculiar deformation of the topological locus, depending on one of the two representations associated with the two components of the link. Most important, we extend the description of this locus to conjugate and, generically, to composite representations and also define the “adjoint” Schur functions emerging in the dual description.

A complex analysis of Yakutsk EAS array data has been performed in order to search for primary photons generating extensive air showers with energies above 10¹⁸ eV. Analyzing calculations and experimental data, selection criteria have been formulated and used to make a sample of showers close in their characteristics to showers initiated by primary photons. An upper limit of the integral photon flux in cosmic rays of extremely high energies has been estimated from these data.

The effect of the viscosity of a liquid on the parameters of standing surface gravity waves in a vertically oscillating rectangular vessel has been experimentally studied. It has been shown for the first time that a 60-fold increase in the viscosity of a working medium as compared to water fundamentally changes the parameters of the second nonlinear wave mode: waves are regularized in the total absence of their breaking. The effect of viscosity on the resonance dependences and process of damping of waves has been studied. The numerical analysis of the dispersion relation for gravity waves has shown that the effects observed in the experiment are due to the presence of short-range perturbations in the cutoff region, where viscous dissipation becomes a dominant factor and short waves are suppressed.

The Landé factors of hyperfine sublevels belonging to the same spectral term differ from each other. This leads to the appearance of an effective gyromagnetic ratio for an atomic ensemble, which can be defined as the ratio of the average magnetic moment to the average angular momentum. Characteristically, this quantity is not a constant, but rather depends on the populations of the hyperfine sublevels. States of an ensemble of atoms occupying their ground level in which the effective gyromagnetic ratio is zero are of much interest. Here, one of such states is considered by the example of alkali metal ⁸⁷Rb. The main idea is to suggest a method for preparing states with zero effective gyromagnetic ratio by means of two-frequency pumping of a saturated alkali-metal vapor in a cell containing a buffer gas. It is noteworthy that, according to calculations, correlation between the two fields is not required for attaining this goal.

Local optical heating and Raman nanothermometry based on resonant silicon particles provide a new promising platform for a number of key nanophotonics applications associated with thermally induced processes at the nano- and microscale. In this work, the crystallization of amorphous silicon nanodisks with optical resonances caused by local optical heating has been studied. The crystallization process is controlled by Raman microspectroscopy. The crystallization temperature of a single nanodisk of about 900 K has been determined under the action of a strongly focused cw laser beam. As a result, an annealed resonant silicon nanoparticle has allowed controlled and reversible heating in the temperature range of 300–1000 K with the possibility of mapping the heating region with submicron spatial resolution.

In the framework of the nonorthogonal tight-binding model, the thermal stability of pentagraphene is studied by numerical simulation using the molecular dynamics technique. Pentagraphene is the recently predicted two-dimensional allotropic modification of carbon, in which the С–С bonds form only pentagons, whereas the hexagons characteristic of carbon nanostructures are absent. It is found that the thermally activated rotation of one С–С bond by an angle of 45° initiates the formation of а defect region, which does not remain localized and rapidly propagates over the whole sample, leading eventually to the total destruction of the sample structure. Nevertheless, the probability of such rotation turns out to be so small that, even at room temperature, pentagraphene can preserve its structure for a fairly long time. This time decreases with the growth of the sample size.