Azimuthal structures of produced particles in heavy-ion interactions

The angular structures of particles produced in ²⁰⁸Pb at 158 A GeV/c and ¹⁹⁷Au at 11.6 A GeV/c induced interactions with Ag(Br) nuclei in emulsion detector have been investigated. Nonstatistical well-ordered ring-like structures of produced particles in azimuthal plane of a collision have been found, and their parameters have been determined. The text was submitted by the authors in English.     

Vortex patterns and nucleation of superconductivity in mesoscopic rectangles and in hybrid superconductor/ferromagnet structures

Nucleation of superconductivity and vortex patterns have been studied in mesoscopic samples providing the crossover between square and rectangular geometries. The measured nucleation line, T _c (H), has been analyzed in the framework of the linearized Ginzburg-Landau theory. A very good agreement has been found between the theoretical T _c (H) boundary and the experimental data for rectangles with different aspect ratios. The superconductor/ferromagnet hybrids, such as magnetic Co/Pd dot in a superconducting loop and the dot on top of a superconducting disk have also been investigated. Pronounced effects of the dot on the T _c (H) boundary have been found, including strong asymmetry with respect to the field polarity.Received: 26 February 2004, Published online: 3 August 2004PACS: 74.25.Dw Superconductivity phase diagrams - 74.78.Na Mesoscopic and nanoscale systems     

The spinning bodies motion stability by lyapunov in an axially symmetric gravitational field

The stability by Lyapunov of the circular motion of spinning test bodies in a Lense-Thirring field has been investigated. For Papapetrou's equations the generalized supplementary conditionsS ^oi U _o =kS ^ij U _j ,k=const.,i, j = 1, 2, 3 have been chosen. Four of the first integrals of motion have been indicated. The existence, stability, and instability regions have been found. It is shown that the positions of stability and instability ranges depend considerably upon the type of supplementary conditions.     

Radiation defect clusters in electron-irradiated silicon

Radiation defect formation in Czochralski-grown (pulled) and vacuum float-zone n-Si (ρ=15 to 150 ωcm) irradiated by electrons with energy E_e=2.5 to 1200 MeV has been studied. The results have been obtained from an analysis of the dose, energy and temperature dependences of the concentration n, Hall mobility μ _n , and charge-carrier lifetime τ. The experimentally observed peculiarities in the variation of n, μ _n , and τ irradiation by electrons with E10 MeV have been explained taking into account the formation of radiation defect clusters in the bulk of the crystal induced by such electrons. The correlation coefficients K_i have bsen obtained which take into consideration the “evolution” of primary displacement cascades in the location of which clusters are formed. The parameters of radiation defect clusters produced by electrons of different energies have been calculated using these coefficients.     

Investigation of two- and three-nucleon transfer reactions in12C +56Fe

Multi-nucleon transfer reactions⁵⁶Fe(¹²C, X) have been studied at an incident¹²C energy of 60 MeV. Angular distributions of¹⁰Be and⁹Be corresponding to 2p and 2p 1n transfer reactions in transition to low-lying states in the residual nuclei have been measured. The angular distribution data for 2p transfer have been analysed in terms of finite range DWBA calculations assuming a one-step transfer of two protons. The spectroscopic factors for three low-lying transitions observed in⁵⁶Fe(¹²C,¹⁰Be)⁵⁸Ni have been extracted. Transfer probabilities for the ground state transition in two- and three-nucleon stripping channels have been obtained and compared with the corresponding sequential transfer probabilities in order to emphasise the role of direct transfer of nucleons vis-a-vis sequential transfer.     

Yrast bands in N = 91 isotones

The in-beam spectroscopy on N = 91 isotones has been carried out using the ¹²C + ¹⁵⁰Nd reaction. The νi _13/2 and νh _11/2 bands of ¹⁵³Sm have been extended up to 33/2⁺ and 31/2^-, respectively. Two new γ-rays have been located on the top of the unfavored band with νi _13/2 configuration in ¹⁵⁷Dy. Two identical relationships have been established in the low-spin region of the yrast νi _13/2 configuration between ¹⁵³Sm and ¹⁵⁵Gd, and between unfavored bands of ¹⁵⁵Gd and ¹⁵⁷Dy. Here all these nuclei have the same neutron number N = 91. Received: 28 June 2000 / Accepted: 20 October 2000     

Thermodynamic conditions for formation of single phase in Bi-superconductor thin films

High quality BSCCO thin films have been fabricated by means of an ion beam sputtering at various substrate temperatures, T_sub, and ozone gas pressures, pO₃. The correlation diagrams of the BSCCO phases appearing against T_sub and pO₃ have been established in the 2212 and 2223 compositional films. In spite of 2212 compositional sputtering, Bi2201 and Bi2223 phases as well as Bi2212 have emerged as stable phases depending on T_sub and pO₃. From these results, the thermodynamic evaluations of ΔH and ΔS, which are related with Gibbs’ free energy change for single Bi2212 or Bi2223 phase have been performed.     

Lithium ions conduction in Li2xMn1-xPS3 films

Li_2xMn_1-xPS₃ films have been synthesized by exfoliating MnPS₃ through the successive intercalations of K⁺ and Li⁺ ions. Their dielectric response has been measured from 80 to 350 K in the frequency range of (10²–10⁶) Hz. The obtained data have been analyzed in terms of both complex permittivity ε* and the ac conductivity σ_ac. The frequency dependence of σ_ac has been interpreted in terms of the Jonscher’s law, whose exponent n decreases by increasing temperature. The n values lie between 0.479 and 0.501 and are typical of materials in which the ac conductivity is due to multiple hops of carriers. By analyzing the σ_dc temperature dependence, the observed dielectric response has been attributed to the intercalated lithium ions, and the Li_2xMn_1-xPS₃ films have been classified as hopping charge carrier systems.     

Momentum distribution and one-body density matrix in liquid3He.

Summary The momentum distributionn(k) and the one-body density matrix ρ₁(r,r' have been calculated in normal liquid³He atT=0. A variational wave function containing two-, three-body and backflow correlations has been used. The Fermi hypernetted chain technique has been employed and the elementary diagrams have been evaluated by the scaling approximation. The present estimate ofn(k) is in good agreement with the Monte Carlo data obtained with similar wave functions.n(k) and the discontinuityZ ofn(k) at the Fermi surface have been computed at several values of the density. The density dependence of the effective massm ^* has been found to be mainly due to that ofZ.     

Stiff Domain Walls in Creation-Field Cosmology

Hoyle-Narlikar C-field has been introduced to study domain walls in Bianchi type-I space-time. The solutions have been studied when the creation field C is a function of time t only. The geometrical and physical aspects for model have also been studied.     

Bianchi Type-I String Cosmological Model in Creation-Field

Hoyle-Narlikar C-field has been introduced to study cosmic strings in Bianchi type-I space-time. The solutions have been studied when the creation field C is a function of time t only. The geometrical and physical aspects for the models have also been studied.     

The proton relaxation of methyl cyanide in the presence of Ni(II) ions,as studied by spin-echo techniques

The proton relaxation times (T ₁ and T ₂) of methyl cyanide, in the presence of Ni(II) ions, have been measured as a function of temperature and frequency by spin-echo techniques. The observed decay times (T ₂?) have also been measured as a function of the separation, t _ep, between the pulses in a Carr-Purcell train of echos. The results obtained in the limit of long pulse separation have been fitted to existing theories. The rotational correlation time of the Ni/MeCN complex, τ _R , the electron spin relaxation time, τ _S , and the distance of closest approach of the protons to the nickel have been estimated from the results. In addition the scalar coupling constant, the exchange rate τ _B and the activation energies for τ _B , τ _S and τ _R have been evaluated. The chemical exchange parameters obtained differ significantly from those obtained by previous workers. There is evidence from the pulse dependence experiments that the complex is a distorted octahedron.     

Rotational structures in 123Cs

High-spin states in ¹²³Cs, populated via the ¹⁰⁰Mo ( ²⁸Si, p4n) fusion-evaporation reaction at E _lab = 130 MeV, have been investigated employing in-beam γ-ray spectroscopic techniques. Rotational bands, built on πg _7/2, πg _9/2 and the unique-parity πh _11/2 orbitals, have been extended and evolve into bands involving rotationally aligned ν(h _11/2)² and π(h _11/2)² quasiparticles. A three-quasiparticle band based on the high-K πh _11/2 ⊗ νg _7/2 ⊗ νh _11/2 configuration has also been observed. Total Routhian Surface (TRS) calculations have been used to predict the nuclear shape parameters ( β₂, β₄, γ) for the various assigned configurations. The assigned configurations have been discussed in the framework of a microscopic theory based on the deformed Hartree-Fock (HF) and angular-momentum projection techniques.     

Investigations of low <Emphasis Type="Italic">q</Emphasis><Subscript><Emphasis Type="Italic">a</Emphasis></Subscript> discharges in the SINP tokamak

Low edge safety factor discharges including very low q _a (1<q _a <2) and ultra low q _a (0<q _a <1) have been obtained in the SINP tokamak. It has been observed that accessibility of these discharges depends crucially on the fast rate of plasma current rise. Several interesting results in terms of different time scales like T _{q a} · τ _R etc have been obtained using a set of softwares developed at SINP. From fluctuation analysis of the external magnetic probe data it has been found that MHD instabilities m=1, n=1 and m=2, n=1 etc. play major role in the evolution of these discharges. To investigate the internal details of these discharges, an internal magnetic probe system has been developed using which current density j _φ and other related parameters have been estimated. By carrying out a resistive stability analysis, evidence of the above-mentioned MHD instabilities have again been found. The physical processes lying behind the accessibility and evolution of the low q _a discharges have been thoroughly investigated.     

ion-implanted junctions and conducting layers in SiC

n-type conducting layers have been formed in n- and p-type hexagonal SiC and n-type cubic SiC by implanting ions from column V of the periodic table; N, P, Sb, or Bi. The implantations were made at room temperature and with energies ranging from 5 to 300 keV. The implanted layers have been evaluated by van der Pauw-Hall effect and sheet resistivity measurements and by scanning electron microscopy for anneal temperatures ranging from 1100 to 1800°C. Type conversion of the implanted layers to n-type has been observed after a 750°C anneal. Considerable lattice reordering is suggested from the observed carrier mobility values after annealing at 1600°C.

We have attempted to form p-type layers in n-type SiC by implanting Re, B, Al, Ga, and Tl. Application of anneal procedures identical to those used to form n-type layers have not resulted in measurable p-type layers.

The p-n junctions formed by the donor-implanted layers have been evaluated as a function of anneal temperature. After annealing at 1200°C there is direct evidence of a thick semi-insulating region between the n-layer and the substrate which produces a p-i-n diode characteristic. The thickness of this i-layer can be substantially reduced with additional annealing, resulting in abrupt junction behavior for the diode.

Well-annealed p-n junctions have been characterized as a function of operating temperature over the range of 23 to 400°C. The forward current-voltage behavior of these diodes is dominated by generation and recombination of the carriers in the depletion layer over most of the temperature range. There is some indication of diffusion currents at the highest temperatures. Avalanche breakdown behavior is observed for reverse bias.

The capacitance-voltage behavior of these diodes as a function of frequency and temperature indicate the presence of a deep level which can be explained in terms of the bulk properties of the material.     

Dynamic-mechanical and nuclear magnetic resonance study of relaxation processes in ultra-high molecular weight polyethylene fibres

The relaxation processes (α, β, and γ) in UHMW PE fibres drawn to different draw ratios λ have been studied by dynamic-mechanical and nuclear magnetic resonance methods. The temperature dependences of tensile loss moduli E″ and spin-lattice relaxation times T ₁ have been analyzed assuming distribution of correlation times τ according to the Davidson—Cole function. The activation energies E _a and parameters ε characterizing widths of distribution, and asymptotic value τ ₀ for correlation times have been determined from experimental data for low-temperature γ-process and for high-temperature α-process. A weak β-process has been found by dynamic-mechanical method and quantitative analysis was made only for fibres with λ = 9. The temperature dependences of second moment M ₂ of the broad-line NMR spectra have been analyzed according to the Gutowsky—Pake formula, which includes only a single correlation time τ _c without distribution. In this case the activation energies E _a and values of τ ₀ have been determined.     

Paramagnetic defects in neutron-irradiated phenakite crystals

Radiation-disordered crystals of phenakite Be₂SiO₄ (at fast neutron fluences of (0.75, 1.0, 1.2, 6.6, 8.5) × 10¹⁸ cm⁻²) have been investigated using EPR spectroscopy. It has been established that the main radiation damages predominantly occur in the silicon-oxygen sublattice of the crystal. Vacancy centers (E′ centers, g = 2.0015), defects of the displaced oxygen type, and O⁻ hole-type centers have been revealed. The paramagnetic absorption signal with the parameters g _x = 2.0218, g _y = 2.0124, and g _z = 2.0027 has been identified with the [SiO₄]³⁻ complex (a variety of O⁻ centers). The intense EPR signals with the parameters g _x = 2.0526, g _y = 2.0020, g _z = 2.0066 and g _x = 2.0290, g _y = 2.0030, g _z = 2.0099 have been assigned to two types of O₂⁻ molecular ions with different local environments. The theoretical models of radiation-induced centers have been discussed by comparing the EPR and optical spectroscopic data.     

Perturbation allowed transitions in the infrared spectrum of 14ND3: determination of the K-dependent parameters in the ground state

ABSTRACT

Accurate values of the K-dependent constants ^{( i )} C, ^{( i )} D_K and ^{( i )} H_K in the ground state of ¹⁴ND₃, with i = s, a, have been determined for the first time thanks to the detections of ‘perturbation allowed’ transitions in the ν₁, ν₂, ν₃, ν₄ and 2ν₄ infrared bands. The rotation–inversion and inversion transitions from the literature, together with 7289 ground state combination differences from the infrared vibration–rotation–inversion transitions have been simultaneously analysed. The adopted rotation–inversion Hamiltonian includes distortion constants up to the eighth power and the Δk = ±3 and Δk = ±6 interaction terms. Precise values of the diagonal constants and of the Δk = ±3 interaction coefficients have been obtained. Accurate values of the ground state term values have been calculated for both s and a levels up to J = 21.     

Low-energy theorems of QCD and bulk viscosity at finite temperature and baryon density in a magnetic field

The nonperturbative QCD vacuum at finite temperature and baryon density in an external magnetic field has been studied. Relations between the nonperturbative condensates and the thermodynamic pressure at T ≠ 0, μ _q ≠ 0, and H ≠ 0 have been obtained and the low-energy theorems have been derived. Bulk viscosity ζ(T, μ, H) has been described in terms of the main thermodynamic quantities characterizing the quark-gluon matter at T ≠ 0, μq ≠ 0, and H ≠ 0. Various limiting cases have been discussed.