Vacuum polarization by a Coulomb center and strong magnetic field. modification of Coulomb's law

The proper time method is used to examine the effect of polarization of the electron-positron vacuum on the nature of the interaction of a charged particle with the field of a nucleus and a magnetic field. It is shown that the interaction of an electron with a nucleus becomes anisotropic in the presence of a magnetic field. The dielectric constants of the vacuum and the effective charge of the Coulomb center are calculated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 38–45, November, 1986.     

Site-specific core level spectroscopy of CO and NO adsorption on Pt(110)(1×2) and (1×1) surfaces

The adsorption of CO and NO on the (1×2) and (1×1) modifications of the Pt(110) surface was studied by x-ray photoemission spectroscopy, LEED and work-function change measurements. The O(1s) binding energy of adsorbed CO is site-specific and differentiates between on-top and bridge adsorbed species. CO adsorption on Pt(110)(1×2) at 120 K occurred sequentially into on-top and bridge sites yielding an orderedc(8×4) layer at the maximum coverage. At 300 K only on-top bonded CO was present after CO adsorption on the (1×2) surface. CO adsorption on the (1×1) surface at 120 K showed a transient bridge adsorbed CO and on-top CO at saturation, with an ordered (2×1)p1g1 LEED pattern. Heating the (2×1)p1g1 CO layer to 400 K also showed this transient bridge CO species. Work function changes generally correlated with the appearance of different CO species but were complex in detail. The findings for CO adsorption are consistent with the missing row model of the (1×2) surface.Parallel data for NO adsorption on (1×2) and (1×1) surfaces at 120 K were less informative than those for CO because O(1s) spectra showed single broad peaks. Peak contributions due to bridge and on-top bonded NO could be estimated.     

Field dependent critical fluctuations aboveT g in the ESR line width of the spin glassAgMn

The ESR of the spin glassAgMn (2.7 and 9.6 at %) has been investigated below and aboveT _g(0.1T _g<T<5T _g) at various microwave frequencies. The analysis yields:1) No explicit frequency dependence but strong magnetic field effects, inherent with ESR-experiments.2) Part of the excess line width is identified as critical spin fluctuations, following a power law. However, because of the presence of the applied field, the reduced temperaturet is not a good scaling variable. We choose the non-linear susceptibility X _s divided byH ², which scales as the order parameter susceptibility. The experiment yieldsW _ex(X _s /H ²) ^p ,p=0.42. From this we deduce z3.     

Simple functional-differential equations for the bound-state wave-function components

We present a new method of a direct derivation of differential equations for the wave-function components of identical-pariticles systems. The method generates in a simple manner all the possible variants of these equations. In some cases they are the differential equations of Faddeev of Yakubovskii. It is shown that the case of the bound states allows to formulate very simple equations for the components which are equivalent to the Schrödinger equation for the complete wave function. The components with a minimal antisymmetry are defined and the corresponding equations are derived.     

Structural changes of Zr x Cu100-x metallic glasses investigated by low temperature specific heat measurements

Amorphous alloys of Zr _x Cu_100–x (55x72) quenched from the melt are investigated by low temperature specific heat measurements. The influence of concentrationx, temperature of the melt before the quenching process and heat treatment on the electronic density of states, the Debye temperature and the superconducting transition temperature is examined. The latter one is the most affected value by structural relaxation while the specific heat in the normal conducting region remains nearly unchanged.     

Thermodynamic properties of ternary semiconducting alloys

Using the new information supplied by extended-x-ray-absorption-fine-structure measurements and the results of our structural model, we compute the bond probability of a few ternary semiconducting III–V and II–VI alloys as a function of temperature and composition in the framework of a modified quasi-chemical approximation. We derive the thermodynamic functions of mixing, considering both elastic and chemical contributions to the bond energies. We examine how the deviation from the full randomness affects the ordering of such alloys and we construct the phase diagrams in the region of phase separation. Possible formation of ordered compounds at low temperatures is predicted.     

Influence of a continuous quenching procedure on the initial stages of spinodal decomposition

Instead of the standard assumption in the theory of phase separation where an instantaneous quench from an initial equilibrium state to the final state in the two-phase region is assumed, we consider the more realistic situation that the change of the external control parameter (e.g. temperature) can only be performed with finite rates. During the initial stages of spinodal decomposition the system then has some memory of the states intermediate between the initial and the final one. This influence of the finite quench rate in continuous quenching procedures is studied within the linearized theory of spinodal decomposition, with the Langer-Baron-Miller decoupling, and with Monte Carlo simulations. Both the case of thermally activated mobilities (applicable to solid metallic alloys) and the case of nearly temperature-independent mobilities (applicable to fluid polymer mixtures) are treated, and possible experimental applications are discussed. We find drastic deviations from the standard instantaneous quench situations in all cases of experimental interest.     

Structure and Thermal Stability of La0.10WO3+y; A Hexagonal Tungsten Bronze Related Phase Formed at High Pressure

The structure and thermal stability of a hexagonal tungsten bronze (HTB) related compound, La_xWO_3+y with x≈0.10 and y≈0.15, has been studied by X-ray diffraction, thermal analysis, and electron microscopy. The structure was refined by the Rietveld method from X-ray powder diffractometer data of a La_0.10WO₃ sample prepared at T=1250°C and P=25 kbar, which consisted of two tungsten bronze related phases in 1:1 proportion. The unit cell dimensions are as follows: La_0.108WO_3+y (y≈0.16), a=7.40890(5), and c=3.79329(4) Å (HTB-related structure); La_0.091WO₃, a=3.82458(6) Å (cubic perovskite tungsten bronze (PTB) structure). The lanthanum atoms in La_0.108WO_3+y are located on the hexagonal axis and statistically distributed on two sites close to the tungsten atom plane. Thermal stability studies of the La_0.10WO₃ sample in an argon atmosphere under ambient pressure conditions revealed that the HTB-related compound is metastable, decomposing to the stable PTB-type structure and WO₃. It was also found from the TG experiments in argon and oxygen that additional oxygen atoms (y) are present in the structure, thus forming a lanthanum tungsten oxide of the above composition. The electron diffraction and microanalysis studies confirmed that crystals of the HTB- and PTB-type structures were formed, with a lanthanum content of x≈0.1.