Perpendicular magnetic anisotropy in single-crystal Co<Subscript>50</Subscript>Pt<Subscript>50</Subscript>/MgO(100) films

The crystal structure and hysteretic magnetic properties of equiatomic single-crystal CoPt films applied on MgO substrates by magnetron sputtering, as well as modification of these properties by thermal annealing, are studied. Heat-treated films of thickness in the range 2<d≤16 nm exhibit perpendicular magnetic anisotropy. A correlation between the crystalline anisotropy constant of the CoPt films and the order parameter of the LI₀ superstructure in these alloys is found. The effect of a single-crystalline MgO substrate on the structure and magnetic properties of equiatomic CoPt films is revealed.     

Estimating the limits of the Fresnel diffraction range for de broglie waves corresponding to particles with Z = 1–2 incident on various nuclei

The aim of this work is to determine the regions where Fresnel diffraction can be observed on different nuclear targets at different energies of the incident particles. The boundaries of the corresponding regions are determined, allowing us to estimate the range of the nuclear targets and the energies of the incident particles upon whose interaction we observe the diffraction effect.     

Determining the statistical weight of multicluster wave functions for light nuclei in a parametrized phase analysis

The experimental angular distributions of light alpha-cluster nuclei are described. Based on fitting, we find that the experimental angular distribution splits into two diffraction modes: the first has a short oscillation period on the nucleus as a whole, and the second has long oscillation periods on the alpha-cluster substructures. Fitting also reveals that the cross sections rising above the Rutherford level for light nuclei is explained by the additivity (modulation) of the alpha-particle mode of elastic scattering (the scattering of alpha particles on alpha-particle clusters).     

Analysis of Bulk and Powdered Samples Using a LAMAS-10M Laser Ionization Time-of-Flight Mass Spectrometer

The problem of the modernization of a LAMAS-10M laser desorption/ionization time-of-flight mass spectrometer was considered, and the methodological fundamentals of the quantitative analysis of bulk and powdered samples by laser desorption/ionization time-of-flight mass spectrometry were discussed. Basic modifications of certain spectrometer units were described, and the reproducibility and accuracy that can be attained using these modifications were estimated. The possibility of the quantitative analysis of bulk samples was demonstrated. These studies were performed using bulk and powdered standard reference materials. In determining precious metals in geological samples, the detection limit for powdered samples was (20–50) × 10^–9. The relative standard deviation for the repeatability of the results (RSD) of the bronze standard reference sample bronza 663 was in the limits RSD = 0.06–0.4% for the major component and 0.5–4.5% for the elements present in percent concentrations. It was shown that the majority of analytes can be determined at a semiquantitative level without using standard reference materials. The key problems of laser desorption/ionization time-of-flight mass spectrometry were considered and methods were proposed to solve these problems. Ways to further improvement of the characteristics of the mass spectrometer were demonstrated.     

Search for hadronic decays of a light Higgs boson in the radiative decay Υ→γA0

We search for hadronic decays of a light Higgs boson (A(0)) produced in radiative decays of an Υ(2S) or Υ(3S) meson, Υ→γA(0). The data have been recorded by the BABAR experiment at the Υ(3S) and Υ(2S) center-of-mass energies and include (121.3±1.2)×10(6) Υ(3S) and (98.3±0.9)×10(6) Υ(2S) mesons. No significant signal is observed. We set 90% confidence level upper limits on the product branching fractions B(Υ(nS)→γA(0))B(A(0)→hadrons) (n=2 or 3) that range from 1×10(-6) for an A(0) mass of 0.3 GeV/c(2) to 8×10(-5) at 7 GeV/c(2).     

Acoustic scattering by turbulent fluctuations of pressure and entropy

Detailed analysis is presented of the well-known Tatarskii’s formula, which describes sound wave scattering in a turbulent atmosphere. The adiabaticity of the acoustic fluctuations and incompressibility of the turbulent fluctuations are assumed only. This yields to additional 1 terms in the classical formula (probably, small in the inertial range of turbulence). We show the change of Obukhov’s formula, which describes the connection between turbulent fluctuations of pressure and velocities in a compressible atmosphere, and also demonstrate the effect of the independence of fluctuations of the potential and thermodynamic temperatures. By analogy with the formula for small-scale isotropic temperature fluctuations, which was also obtained by Obukhov, we derive a formula for the fluctuations of entropy and potential density as function of entropy, which describes spatial distribution of the probability density of identical “fluid particles” in the turbulent media.     

Effect of residual gas on the ion charge distribution in vacuum arc discharge plasmas

A magnetic mass analyzer and time-of-flight mass spectrometer are used to study the effect of the pressure and type of residual gas on the ion charge distribution in the plasma of an arc discharge with a cathode spot. The possibility of ionizing a substantial fraction of the gas atoms in this type of discharge is pointed out. Zh. Tekh. Fiz. 68, 24–28 (September 1998)     

Global unsolvability of a nonlinear conductor model in the quasistationary approximation

We study initial-boundary value problems for a model differential equation in a bounded region with a quadratic nonlinearity of a special type typical for the theory of conductors. Using the test function method, we show that such a nonlinearity can lead to global unsolvability with respect to time, which from the physical standpoint means an electrical breakdown of the conductor in a finite time. For the simplest test functions, we obtain sufficient conditions for the unsolvability of the model problems and estimates of the blowup rate and time. With concrete examples, we demonstrate the possibility of using the method for one-, two- and three-dimensional problems with classical and nonclassical boundary conditions. We separately consider the Neumann and Navier problems in bounded R ^N regions (N ≥ 2).     

Sea-level muon spectrum in the energy range 1–10 TeV from the data of underground experiments

Within an adjoint approach, the properties of the muon component in various types of rock and in water are calculated with allowance for fluctuations of energy losses in all muon-interaction processes. The behavior of the muon spectrum at sea level is established on the basis of a comparison of the muonabsorption curves obtained in this way and experimental data from underground facilities. It is shown that the deficit of the calculated muon flux obtained with the aid of data from direct measurements of the spectra of primary nuclei and Reggeon models of nuclear interactions is not less than 50% in the energy range 1–10 TeV.     

Charge-state distribution of ions in a vacuum arc discharge plasma in a high magnetic field

It is shown that the fraction of multiply charged metal ions generated in a vacuum arc discharge plasma grows substantially in a high magnetic field. This effect was observed for more than 30 different cathode materials. A relation is established between growth of the mean charge of the ions and increases in the burning voltage of the arc. It is demonstrated that the burning voltage of the vacuum arc can be ultimately increased to 160 V. Zh. Tekh. Fiz. 68, 39–43 (May 1998)