Electronic state of ruthenium deposited onto oxide supports: An XPS study taking into account the final state effects

The electronic state of ruthenium in the supported Ru/EO_x (EO_x = MgO, Al₂O₃ or SiO₂) catalysts prepared by with the use of Ru(OH)Cl₃ or Ru(acac)₃ (acac = acetylacetonate) and reduced with H₂ at 723 K is characterized by X-ray photoelectron spectroscopy (XPS) in the Ru 3d, Cl 2p and O 1s regions. The influence of the final state effects (the differential charging and variation of the relaxation energy) on the binding energy (BE) of Ru 3d_5/2 core level measured for supported Ru nanoparticles is estimated by comparison of the Fermi levels and the modified Auger parameters determined for the Ru/EO_x samples with the corresponding characteristics of the bulk Ru metal. It is found that the negative shift of the Ru 3d_5/2 peak which is observed in the spectrum of ruthenium deposited onto MgO (BE = 279.5-279.7 eV) with respect to that of Ru black (BE = 280.2 eV) or ruthenium supported on γ-Al₂O₃ and SiO₂ (BE = 280.4 eV) is caused not by the transfer of electron density from basic sites of MgO, as considered earlier, but by the differential charging of the supported Ru particles compared with the support surface. Correction for the differential charging value reveals that the initial state energies of ruthenium in the Ru/EO_x systems are almost identical (BE = 280.5 ± 0.1 eV) irrespectively of acid-base properties of the support, the mean size of supported Ru crystallites (within the range of 2-10 nm) and the surface Cl content. The results obtained suggest that the difference in ammonia synthesis activity between the Ru catalysts supported on MgO and on the acidic supports is accounted for by not different electronic state of ruthenium on the surface of these oxides but by some other reasons.     

Nonlinear nonstationary theory of light propagation through a resonance medium taking into account optical pumping of atoms

The general nonstationary theory of propagation of an elliptically polarized pulse resonantly interacting with the 1/2–1/2 transition is presented. The theory that takes into account relaxation processes is developed in terms of irreducible tensor operator representation allowing diagonalization of the relaxation matrix and introduction of effective decay times governing relaxation of both population and coherence between magnetic sublevels of the resonant system. It is shown that interference of magnetic sublevels in the field of polarized radiation that optically pumps the atoms can result in inversionless amplification of radiation.     

Superradiant Rayleigh scattering of light from a Bose-Einstein condensate of dilute atomic gases, taking into account backward recoil momentum

An extension of the semiclassical model is proposed for superradiant Rayleigh scattering of light from a Bose-Einstein condensate of dilute atomic gases. In contrast to the familiar models, this model takes into account the fact that the atom may be excited by the scattered light and may acquire backward recoil momentum. The presented equations are solved analytically for the initial (linear) stage of the process. The intensity of the scattered light and the efficiency of populating atomic states with different momentum values are studied as a function of detuning from resonance. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 1, pp. 65–72, January–February, 2006.     

Collisional perturbation of resonance fluorescence from atoms in a strong monochromatic driving field

We treat the problem of collisional perturbation of resonance fluorescence by means of a fully quantum-mechanical master equation approach based on the Fano-Zwanzig projection operator method. We suppose monochromatic irradiation at arbitrary intensity and consider mainly the two-state atom approximation. In the weak-coupling case, defined by assuming that the collision operator does not depend on the coupling with the exciting field, we recover results of previous work, valid beyond the restrictions of the impact limit.     

Photofield ionization of deep centers in semiconductors,taking Coulomb-field effects into account

The electrical-absorption coefficient in semiconductors is calculated for the case of charge-carrier transition from a deep level to the closest level at the base of a Hulthen model potential, including both short-range and long-range (Coulomb) components. The effect of the Coulomb field on the electron wave function in the conduction band is taken into account.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 85–91, December, 1977.     

IR signature estimation of an object or a target by taking into account atmospheric effects

In this study, a reference infrared (IR) image of an object or a target was analyzed, and the IR signature was calculated. Background and atmospheric effects were decomposed so that the calculation errors were minimized. Depending on the reference IR image, the IR signature at any distance and any angle was estimated while considering atmospheric effects. Calculated results were obtained from IR images taken from the same distance and angle, and were compared with the estimated results. The comparison of the measured and calculated signatures demonstrated the accuracy of the proposed method of estimation.     

Leontovich-Levin equation taking into account finite conductivity of a conductor

A generalization of the Leontovich-Levin equation for current in an ideally conducting linear vibrator to the case of a finite-conductivity conductor is considered. This generalization is valid for strong and weak skin effects, as well as for inhomogeneous conductors with an axisymmetric conductivity distribution (in particular, for carbon nanotubes, CNTs). The internal structure of the conductor is fully described by the internal impedance per unit length. A recurrent scheme is proposed for calculating such an impedance for layer-inhomogeneous conductors. A particular case of the impedance for metallic achiral CNTs is considered, and substantial differences between this case and the macroscopic model of a conductor with full skin effect are indicated.     

A single-particle nonlocal potential for taking into account quantum-electrodynamic corrections in calculations of the electronic structure of atoms

A new single-particle effective potential is proposed. This potential allows one to take into account quantum-electrodynamic (QED) corrections in relativistic calculations of many-electron ions and neutral atoms. In particular, it can be used in the Dirac-Fock (DF) method, the relativistic density functional, the multiconfiguration DF method, and the relativistic method of superposition of configurations. The potential is constructed without fitting parameters. Self-energy corrections have been calculated for a number of neutral alkali atoms and Li-like ions to check the quality of the nonlocal potential proposed. Comparison with the data in the literature on the QED corrections obtained in nonempirical calculations based on the use of QED perturbation theory is performed.     

Analysis of oscillations of concentration in bounded binary mixtures taking into account surface effects

We consider a binary mixture bordering a substrate and vacuum and forming a film. The distribution of one of the mixture components is described by the Cahn-Hillard equation with asymmetric boundary conditions taking into account (wetting) processes occurring at the boundary and in surface layers of the film and, probably, the effect of a constant external magnetic field. The parameters of the problem characterize the bulk correlation length, pair interaction intensity in the nearest neighbor approximation at the film boundary, and the renormalized magnetic field acting on the spins in the surface layers of the system. The range of parameters generating oscillations of the concentration over the film thickness is determined. Subranges of parameters generating the preset number of oscillations over the film cross section are indicated. The analytic results are qualitatively confirmed in numerical experiments.     

Cooperative population dynamics of an ensemble of Λ atoms in a bichromatic field

Equations are derived which describe the dynamics of three-level atoms with a Λ level scheme, interacting with two coherent resonance fields under conditions such that cooperative relaxation predominates over incoherent spontaneous emission. A numerical calculation of the temporal dynamics of the values of the atomic populations is performed. It is shown that coherent population trapping in the presence of cooperative decay is possible. The quantities characterizing this phenomenon are calculated—the width of the black line and the transition time to coherent trapping in this scheme. Zh. Tekh. Fiz. 68, 19–24 (June 1998)     

An improvement of the Peierls equation by taking into account the lattice effects

An improvement of the Peierls equation has been made by including the lattice effects. By using the non-trivially gluing mechanism for the simple cubic lattice, in which atoms interact with its first and second nearest neighbours through a central force, the dislocation equation has been derived rigorously for the isotropic case. In the slowly varying approximation, the Peierls equation with the improvement by including the lattice effects has been obtained explicitly. The new equation can be used to substitute for the old one in theoretical investigations of dislocations. The major change of the predicted dislocation structure is in the core region. The width of the dislocation given by using the new equation is about three times that given by the classical Peierls--Nabarro theory for the simple cubic lattice.     

Electron energy spectrum in thin films,taking into account an arbitrary one-dimensional internal field

A compact and accurate solution of the specified problem is obtained in the model of an infinitely deep potential well. The solution is expressed in terms of the one-dimensional Green's function for an electron in an arbitrary field in the absence of film boundaries. The one-dimensional problem may be generalized to the three-dimensional case when the three-dimensional field allows separation of variables along and perpendicular to the plane of the film. The case of a periodic field is examined in more detail. It is shown that in the forbidden band of a bulk crystal there arise permitted film subbands.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 7–11, May, 1977.Thanks are due to V. L. Boneh-Bruevich for discussion of the work and for useful comments.     

一种考虑声线弯曲的温度场重建算法

声波在非均匀温度场中传播时会由于声波的折射而产生声线弯曲现象。为提高非均匀温度场声学CT (Computer Tomography)重建精度,提出一种考虑声线弯曲的重建算法。首先用最小二乘法获得一个不考虑声线弯曲的重建温度场,然后用打靶-插值法确定本征声线出射角,用三角形前向展开法追踪声线,获得此温度场中声波发射/接收器间的本征声线,建立本征声线上声波传播时间与温度分布间的关系,进而实现考虑声线弯曲的最小二乘法温度场重建。单峰、双峰温度场仿真重建结果表明:所采用的本征声线追踪法计算简单运行速度快;考虑声线弯曲后,可明显提高温度场重建精度。因此所提重建算法能更好地适应实际温度场重建需求。     

Conditions for self-excitation of a gyrotron taking space charge into account

Institute of Applied Physics, Academy of Sciences of the USSR. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 32, No. 11, pp. 1408–1416, November, 1989.     

An inflationary scenario taking into account of possible dark energy effects in the early universe

We investigate the possible effect of cosmological-constant type dark energy during the inflation period of the early universe. This is accommodated by a new dispersion relation in de Sitter space. The modified inflation model of a minimally coupled scalar field is still able to yield an observation-compatible scale-invariant primordial spectrum, simultaneously having the potential to generate a spectrum with lower power at large scales. A qualitative match to the WMAP 7-year data is presented. We obtain an Ω _Λ of the same order of that in the Λ-CDM model. Possible relations between the de Sitter scenario and Doubly Special Relativity (DSR) are also discussed.     

Quantum-electrodynamic effects for atoms in a laser field

Quantum-electrodynamic radiation corrections to atomic energy levels in the presence of monochromatic laser field are considered as radiation shifts of quasienergies. General expressions are obtained for self-energy part of radiation shifts for an arbitrary multilevel atomic system. As an appendix, the radiation shifts of spectral lines of atomic resonance transitions are investigated.     

Double scattering approximation of the atmospheric laser location equation taking polarization effects into account

An equation is obtained for the Stokes vector of radiation twice scattered in the backwards direction, assuming that the transmitter and receiver have small angular apertures, that the pulse length is short, and that the receiver and the transmitter are monostatically placed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 1, pp. 80–85, January, 1976.