Heating of ultracold neutrons on beryllium surfaces

The temperature dependence of the loss factor for ultracold neutrons owing to heating at thermal energies on the surface of a beryllium sample is studied. The probability of heating ultracold neutrons is anomalously high throughout the entire measured temperature interval, but especially at low temperatures. Zh. éksp. Teor. Fiz. 114, 786–797 (September 1998)     

Investigation of special features of the neutron and proton shell structure of the isotopes 90,92,94,96Zr

The neutron and proton single-particle energies and the occupation probabilities for the valence states of the even-even isotopes ^90,92,94,96Zr are determined by matching data on nucleon-stripping and nucleon-pickup reactions on the same nucleus. The data obtained in this way suggest the magicity of the number N = 56 for Z = 40. The single-particle energies of all bound neutron and proton states in the ^90,92,94,96Zr nuclei are described within the experimental errors on the basis of the dispersive optical model.     

Macroscopic quantum tunneling in "small" Josephson junctions in a magnetic field

We study the phenomenon of macroscopic quantum tunneling (MQT) in small Josephson junctions (JJ) with an externally applied magnetic field. The latter results in the appearance of the Fraunhofer type modulation of the current density along the barrier. The problem of MQT for a pointlike JJ is reduced to the motion of the quantum particle in the washboard potential. In the case of a finite size JJ under consideration, this problem corresponds to a MQT in a potential which itself, besides the phase, depends on space variables. The general expression for the crossover temperature T0 between thermally activated and macroscopic quantum tunneling regimes and the escaping time tau(esc) have been calculated.     

Disproportionation of 2,5-dichlorosemiquinone radicals in benzene according to unsteady-state kinetic data for the chain reaction between 2,5-dichlorohydroquinone and <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>′-diphenyl-1,4-benzoquinone diimine

A method for determining the rate constant of disproportionation of 2,5-dichlorosemiquinone radicals (k ₆) from unsteady-state kinetic data for the initiated chain reaction of N,N′-diphenyl-1,4-benzoquinone diimine with 2,5-dichlorohydroquinone have been developed, and two variants of this method are presented. The method is based on the study of the unsteady-state disappearance kinetics of one of the initial reactants (quinone diimine) in its initiated chain reaction with hydroquinone. The unsteadiness of the reaction is due to the presence of semiquinone radicals or initiator radicals accumulated before the start of the reaction at a concentration exceeding the steady-state concentration of semiquinone radicals in the chain reaction. The variants of the method differ in the order of mixing the reactants and initiator, on which the nature and concentration of the radicals accumulated in the system before the reaction depend. In the first variant, a quinone diimine + initiator solution is initially prepared and initiator radicals are accumulated. Hydroquinone is added to this solution (start of the reaction). In the second variant, a hydroquinone + initiator solution is initially prepared and semiquinone radicals from hydroquinone are accumulated. Quinone imine is then added to the solution (start of the reaction). The disproportionation rate constant of semiquinone radicals (k ₆) is derived from the dependence of the decrease in the quinone imine concentration in a certain short time (∼20 s) after the start of the reaction on the initiation rate. The rate constant k ₆ in benzene is (7.3 ± 3.7) × 10⁶ l mol⁻¹ s⁻¹ according to the first variant of the method and (5.0 ± 2.2) × 10⁶ l mol⁻¹ s⁻¹ according to the second one.     

Application of Grid technology in computational chemistry

The key trends and prospects of development of computational chemistry that formed in the early 2010s are considered. The most advanced methods for solution of various types of challenges in the computational and quantum chemistry by calculations in the distributed environments (Grid) and on high-performance supercomputer installations and the application methods of parallel and distributed computations are demonstrated; the tailor-made technologies developed for these calculations are described.     

Integrals containing products of Airy functions and planar photon propagation in a magnetic field

We derive a number of new results on integrals of products of Airy functions, using various integral transform techniques. As an application, we deduce a compact integral representation, suitable for numerical integration, of the one‐loop photon propagator in a magnetic field in 2 + 1 dimensional scalar quantum electrodynamics. Copyright © 2011 John Wiley & Sons, Ltd.     

Effects of redox thermal treatments on the transverse resistance peak at the edge of the superconducting transition in Bi2Sr2CaCu2O8+x

The growth of the transverse resistivity just above the transition in Bi₂Sr₂CaCu₂O_8+x (BSCCO 2212) expitaxial films is studied in the framework of the recent fluctuation model proposed by Ioffe, Larkin, Varlamov and Yu Lu. The effects of different redox thermal treatments on the transverse resistive peak is investigated. The fit of the experimental curves with the theory is good and allows one to estimate the values of some physical parameters included in the theory itself (namely the in-plane Fermi velocity ν_F, the carrier lifetime τ and the hopping integral w). It is shown that the oxidizing thermal treatment gives rise to a strong decrease in the transverse resistance peak just above T_c. Such effect is ascribed to the increase in ν_F due to the growth of the carrier concentration induced by the oxidizing treatment. Effects on the carrier lifetime and the hopping integral are hindered by the large variation of ν_F.     

Convolution of Rayleigh functions with respect to the Bessel index

A convolution of Rayleigh functions with respect to the Bessel index can be treated as a special function in its own right. It appears in constructing global-in-time solutions for some semilinear evolution equations in circular domains and may control the smoothing effect due to nonlinearity. An explicit representation for it is derived which involves the special function ψ(x) (the logarithmic derivative of the Γ-function). The properties of the convolution in question are established. Asymptotic expansions for small and large values of the argument are obtained and the graph is presented.