Low energy universality and scaling of Van der Waals forces

At long distances interactions between neutral ground state atoms can be described by the Van der Waals potential V(r) =-C6/r^6-C8/r^8 - ... . In the ultra-cold regime atom-atom scattering is dominated by s-waves phase shifts given by an effective range expansion p cot d0 (p) = -1/a0 + r0 p^2/2 + ... in terms of the scattering length a0 and the effective range r0. We show that while for these potentials the scattering length cannot be predicted, the effective range is given by the universal low energy theorem r0 = A + B/a0+ C/a0^2 where A,B and C depend on the dispersion coefficients Cn and the reduced di-atom mass. We confront this formula to about a hundred determinations of r0 and a0 and show why the result is dominated by the leading dispersion coefficient C6. Universality and scaling extends much beyond naive dimensional analysis estimates.Comment: 4 pages, 3 figure

Efimov states in asymmetric systems

The conditions for occurrence of the Efimov effect is briefly described using hyperspherical coordinates. The strength of the effective hyperradial $\rho^{-2}$ potential appearing for two or three large scattering lengths is computed and discussed as function of two independent mass ratios of the three constituent particles. The effect is by far most pronounced for asymmetric systems with three very different masses. One Efimov state may by chance appear in nuclei. Many states could be present for systems with one electron and two neutral atoms or molecules. Estimates of the number of states and their sizes and energies are given.Comment: 7 pages, 3 figure

Numercal simulation of dynamic channel-angular pressing of copper specimens in 3D statement

Severe plastic deformation of copper specimens during dynamic channel-angular pressin

Microstructure and properties of nanocomposite Al-Si-N system coatings produced by magnetron sputtering

The paper presents the results of investigations of the structural and phase conditions, mechanical and optical properties of Al-Si-N system coating obtained by magnetron sputtering. The thickness of this coating ranges from 3 to 19 µm and is sprayed on silica glass using magnetron sputtering technique. The formation of nanoscale AlN single phase with HCP crystal system and the crystal grain size of up to 20 nm is discovered using the X-ray diffraction method. The texture of [002] orientation is observed in the structure of Al-Si-N-based coatings. These coatings are characterized by high values of microhardness and coefficient of restitution. The transmission spectrum of the coatings are produced within the range of 190-1100 nm. Al-Si-N-based coatings are characterized by a high degree of transparency (≈ 80%) within the visible light spectrum and complete opaqueness in the ultraviolet region. The refractive index and the thickness of Al-Si-N system coating are determined using the transmission spectrum and refractive index. The refractive index of Al-Si-N-coated glass samples is determined using the transmission spectrum the value of which increases with the increase in the coating thickness

Structure and optical-mechanical properties of the Zr-Y-O coatings deposited by pulse magnetron sputtering on optical glass

The results of the research of the phase composition and the mechanical properties of the coatings on the basis of the Zr-Y-O system produced by pulsed magnetron sputtering on the K208 glass substrates are presented in this paper. By the X-ray diffraction method it has been discovered that there is the ZrO2 phase in two modifications in the coatings. The deposition of the Zr-Y-O coating system allows not only to increasing the microhardness of the surface layer of the K208 glass up to ~19 GPa, but also maintain a high level of the elastic properties (We> 0.70). The laboratory tests have been carried out on the impact of the high-speed flows of iron microparticles on the Zr-Y-O protective coating produced by pulsed magnetron sputtering. When a high-speed flow of iron microparticles impact the samples with the Zr-Y-O coatings the surface density of the craters decreases ~ 7 times compared with initial state

Superconducting and magnetic properties of a new EuAsFeO0.85F0.15 superconductor

Polycrystalline samples of a new superconducting EuAsFeO0.85F0.15 compound with critical temperature Tc=11K were prepared by solid state synthesis. Its electric and magnetic properties have been investigated in magnetic fields from 0.1 to 140000 Oe. Critical magnetic fields Hc1, and Hc2 were measured and hence the magnetic penetration depths and the coherence length have been estimated. The temperature dependence Hc2 (T) exhibits clear hyperbolic - type behavior starting with the lowest fields. The data derived were used to estimate probable high Tc and Hc2 in compounds doped with rare-earths having small atomic radii.Comment: 12 pages, 10 figures, 13 reference