Resonant photoemission in DyNi2Mn x rare-earth intermetallides

The electronic structure of the DyNi₂Mn _x rare-earth (RE) intermetallides whose cubic structure is similar to the structure of RT₂ compounds is studied. Resonant photoemission and X-ray absorption methods are used in the vicinity of the 2p- and 3p-excitation thresholds of transition elements and the 3p-, 3d-, and 4d-thresholds of RE metals to find the Ni, Mn 3d-, and R 4f-partial densities of the states in the valent band. The use of resonant photoemission allows us to establish features of the interaction between the unfinished 4f-shells of ions of RE metals with ions of the transition 3d-elements in RNi₂Mn _x compounds. The contributions from atoms of various elements to the structure of the valent band are separated, and the basic regularities of band formation during the introduction of manganese atoms are found.     

Numerical estimates for stability domains of Lagrangian solutions to the restricted three-body problem

The geometric parameters of stability domains of Lagrangian solutions to the classical restricted three-body problem are quantitatively estimated. It is shown that these domains are ellipsoid-like plane figures stretched along the tangent to the circle that passes through the Lagrangian triangle solutions. A heuristic algorithm is proposed for determining the maximum size of these domains of attraction.     

Role of Nondipole Transitions in Formation of K-Edge Extended Electron Energy Loss Fine Structure

For extended electron energy loss fine structure (EELFS) in the case of ionized K-level, the effects of nondipole processes are estimated at different excitation energies and scattering angles of incident electron. A multiplet resolution converging fast for any scattering angles of incident electron is suggested, and simple analytical expressions up to the quadrupole term are derived. Using these estimates, we have calculated the Al K-edge EELFS spectrum and compared the calculated data with the experimental results. The problem of violation of the dispersion law of secondary electrons is discussed; this problem is caused by the finite lifetime of the excited electronic subsystem of the sample compared to the dispersion law of free electrons.     

Molecular structure of polymeric materials and sorption of water vapor

Methods for calculating the coefficients of the thermal equation of water vapor sorption by polymeric materials were developed. These methods enable calculation of the equilibrium amounts of sorption in a wide temperature range from the cohesion energy of a polymer.     

TPD studies of benzene adsorption over vanadium-molybdenum oxide catalysts

Benzene is shown to be adsorbed on the surface of a V₂O₅-MoO₃ catalyst in two forms. The activation energies of benzene desorption for its first and second forms are 50 and 134 kJ/mol, respectively, in the latter case the adsorption proceeding with dissociation.

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Optimal Disturbances of Bistable Time-Delay Systems Modeling Virus Infections

For bistable time-delay dynamical systems modeling the dynamics of viral infections and the virusinduced immune response, an efficient approach is proposed for constructing optimal disturbances of steady states with a high viral load that transfer the system to a state with a low viral load. Functions approximating the behavior of drugs within the framework of well-known pharmacokinetic models are used as basis functions. Optimal disturbances are sought in the W ₂ ¹ norm. It is shown that optimal disturbances found in this norm are superior to those found in the L₂ norm as applied to the development of adequate therapeutic strategies.     

Shape of the X-Ray photoelectron spectra of inner levels: An L + 1 rule for electron—hole excitations

Intercalated Ni_0.5TiTe₂ compound was studied by X-ray phot oelectron spectroscopy. The shape of the inner-level lines and the magnitude of the electron—hole interaction effects on the component atoms were analyzed. A rule was formulated for the many-electro n excitations induced in solids by a photohole.     

Spin fluctuations and Curie temperature in the compounds R2M17 with nonmagnetic elements

The magnetic properties of materials for permanent magnets based on binary compounds R₂M₁₇ (R=Y, Sm; M=Fe, Co), also including additions of the nonmagnetic elements N, Al, and Si, are investigated a the theory of dynamical fluctuations of the electronic spin density. It is shown that the Curie temperature is determined by the ratio of the exchange splitting energy (proportional to the magnetization at T=0) and the rms value of the fluctuations (proportional to the local spin susceptibility). The fluctuations are much larger in iron compounds than in cobalt alloys. This results not only in quantitative differences in their characteristics but also in a qualitatively different change in the properties of these materials on nitriding. Fiz. Tverd. Tela (St. Petersburg) 41, 77–83 (January 1999)