Tashkent, Uzbekistan
Tashkent, Uzbekistan

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Umarov F.F.,Kazakh-British Technical University | Dzhurakhalov A.A.,Arifov Institute of Electronics | Dzhurakhalov A.A.,University of Antwerp
Surface and Interface Analysis | Year: 2013

The peculiarities of sputtering processes at low-energy Ne grazing ion bombardment of Si(001), SiC(001) and Cu3Au(001) surfaces and their possible application for the surface modification have been studied by computer simulation. Sputtering yields in the primary knock-on recoil atoms regime versus the initial energy of incident ions (0.5-5 keV) and angle of incidence (0-30°) with respect to the target surface have been calculated. It was shown that in the case of grazing ion bombardment, the layer-by-layer sputtering is possible, and its optimum is observed within the small angular range of the glancing angles near the threshold sputtering angle. Comparative studies of layer-by-layer sputtering for Si(001) and SiC(001) surfaces versus the initial energy of incident ions as well as an effective sputtering and sputtering threshold are discussed. Copyright © 2012 John Wiley & Sons, Ltd. Copyright © 2012 John Wiley & Sons, Ltd.

Amusia M.Y.,Hebrew University of Jerusalem | Amusia M.Y.,RAS Ioffe Physical - Technical Institute | Baltenkov A.S.,Hebrew University of Jerusalem | Baltenkov A.S.,Arifov Institute of Electronics
Central European Journal of Physics | Year: 2010

We demonstrate, using a simple model, that, in the frame of muffin-tin-like potential, non-physical peculiarities appear in molecular photoionization cross-sections that are a consequence of "jumps" in the potential and its first derivative at some radius. The magnitude of non-physical effects is of the same order as the physical oscillations in the cross-section of a diatomicmolecule. The role of the size of these "jumps" is illustrated by choosing three values for it. The results obtained are connected to the previously studied effect of non-analytic behavior as a function of r, the potential V(r) acting upon a particle on its photoionization cross-section. In reality, such potential has to be analytic in magnitude and have a first derivative function in r. The introduction of non-analytic features in model V(r) leads to non-physical features - oscillations, additional maxima, and so forth - in the corresponding cross-section. © 2009 Versita Warsaw and Springer-Verlag Berlin Heidelberg.

Isakhanov Z.A.,Arifov Institute of Electronics
Journal of Surface Investigation | Year: 2013

The angular and energy distributions of alkaline Na+ and K+ ions which have passed through thin Cu films in different crystal states are studied. The ion energy E0 is varied from 10 to 40 keV, and the incidence angle. ranges from 0° to 60°. The angular aperture of the detector is ∼0.5°, which allows the form of the angular distribution of ions which have passed through the solid thin films as a function of the energy, the angle of primary-ion beam incidence, and the layer thickness to be studied in detail. It is shown that, in the range E0 = 10.40 keV, the energy loss ΔE of those ions that have passed increases linearly as the energy of incident ions increases. The energy loss increases with increasing ion mass in the case of singly charged ions. The surface amorphization of single- and polycrystalline films leads to an increase (by 150-200 eV) in the energy loss caused by the diffuse propagation of ions and to loss-peak broadening. It is probable that surface amorphization is accompanied by an increase in the number of atoms experiencing multiple collisions with atoms of the film, which leads to an increase in the average energy loss by ions that have passed through films. © 2013 Pleiades Publishing, Ltd.

Amusia M.Y.,Hebrew University of Jerusalem | Amusia M.Y.,RAS Ioffe Physical - Technical Institute | Baltenkov A.S.,Arifov Institute of Electronics
JETP Letters | Year: 2011

The special features of magneto-dipole photoionization of atomic s states are analyzed and the possibilities of experimental observation of this effect are discussed. It has been shown that despite the smallness of total cross sections for magnetic processes as compared with electric-dipole ones, the experimental observation of magnetic effects is possible, in principle, if photoelectrons are detected in the directions perpendicular to both the polarization vector of photon and its momentum; i. e. in the directions where the differential cross section for electric-dipole ionization of atomic s states is close to zero. The capabilities of the derived general formulas for the magneto-dipole cross sections are illustrated by numerical calculations for s subshells of He and Be atoms. © 2011 Pleiades Publishing, Ltd.

Usmanov D.,Arifov Institute of Electronics | Khasanov U.,Arifov Institute of Electronics | Pantsirev A.,Arifov Institute of Electronics | Van Bocxlaer J.,Ghent University
Journal of Pharmaceutical and Biomedical Analysis | Year: 2010

This paper provides the development of analytical capabilities of surface-ionization mass spectrometry (SI/MS) and high performance liquid chromatography with tandem mass spectrometry (HPLC/MS/MS) for narcotic analgesic omnoponum, which perfectly exemplifies a mixture of opium alkaloids. It has been revealed that the investigated opiates solution, omnoponum, is ionized by the surface ionization (SI) method with high sensitivity. In the SI mass spectrum, M +, (M-H) +, (M-H-2nH) +, (M-R) + and (M-R-2nH) + ion lines, where M is a molecule, H is the hydrogen atom and R is a radical, were observed. These ion lines consist of combined omnoponum mixture SI mass spectra, i.e. morphine, codeine, thebaine, papaverine, and narcotine. Moreover, while the study of omnoponum by HPLC/MS/MS methods has attested that the mixture really consists of 5 components, it has been demonstrated that the SI/MS method can be utilized for the analysis of this mixture without the necessity of its chromatographic separation. © 2010 Elsevier B.V.

Baltenkov A.S.,Arifov Institute of Electronics | Becker U.,Fritz Haber Institute | Manson S.T.,Georgia State University | Msezane A.Z.,Clark Atlanta University
Journal of Physics B: Atomic, Molecular and Optical Physics | Year: 2010

Within the framework of a model representing the potential of a C 60 cage as a spherical electro-neutral layer U(r) formed by smeared carbon atoms, the effect of the details of the potential on spectral characteristics of atoms localized inside the fullerene shell has been studied. Using examples of encapsulated H and He atoms, it is shown that for potential shell thickness not exceeding 1.3-1.5 au, confinement resonance oscillations in the photoionization cross section weakly depend on the shape of the function U(r). With increasing width of the potential well, the confinement resonances in the energy dependence of the photoionization cross section disappear. In addition, it is demonstrated that displacing the doped atom from the centre of the cavity also diminishes the amplitude of the confinement resonance. © 2010 IOP Publishing Ltd.

Baltenkov A.S.,Arifov Institute of Electronics | Becker U.,Fritz Haber Institute | Manson S.T.,Georgia State University | Msezane A.Z.,Clark Atlanta University
Journal of Physics B: Atomic, Molecular and Optical Physics | Year: 2012

The photoabsorption by an electron bound by a two-centre potential has been investigated within the framework of the zero-range potential model. Expressions for total photoabsorption cross sections and for the photoelectron angular distributions have been derived for fixed-in-space and randomly oriented targets. The analytical formulae for gerade and ungerade molecular states have been used to analyse separately the molecular effects due to the two-centre ground state of quasi-molecule and diffraction effects that are connected with the spherical waves in the molecular continuum. It is shown that the interference of these waves significantly influences the magnitude of the cross sections near threshold but does not significantly distort the shape of the photoelectron angular distribution and it depends rather weakly on the character of the forces acting between the electron and molecular residue: Coulomb forces for neutral molecular photoionization or the short-range forces in the case of photodetachment of molecular negative ions. It is shown that despite the fact that the photoionization of diatomic molecules is reminiscent of Young's double-slit experiment, the similarity between these processes has been grossly exaggerated. This is confirmed by comparing the results of the classical interference of an electron scattered by two spatially separated centres with molecular photoelectron angular distributions. © 2012 IOP Publishing Ltd.

Baltenkov A.S.,Arifov Institute of Electronics | Manson S.T.,Georgia State University | Msezane A.Z.,Clark Atlanta University
Central European Journal of Physics | Year: 2011

A comprehensive study is undertaken of angular distributions of electron knock-out from atomic targets by fast electrons with a small transfer of momentum. The general expressions for the parameters of the triple differential cross-section of impact ionization in the optical limit are derived. The calculated parameters are compared with those of the angular distribution of electrons ejected from an atom in the process of photoionization. In these processes, when the multipole transitions are involved, the one-to-one correspondence between the photoionization and impact ionization parameters disappears. The nondipole transitions lead to the backward/forward asymmetry of the angular distribution of ejected electrons that is absent in the dipole approximation for ionization by both fast electrons and photons. Using the He atom as an example, the character of the asymmetry for these two processes is qualitatively different and the backward/forward asymmetry results in macroscopic directed motion of secondary electrons accompanying the passing of a fast electron beam through gas or plasma. The general formulas for this drag current are derived and applied to gaseous He. © 2011 Versita Warsaw and Springer-Verlag Wien.

Morozov S.N.,Arifov Institute of Electronics | Rasulev U.Kh.,Arifov Institute of Electronics
Surface and Interface Analysis | Year: 2013

A surface-ionization method of measuring the total sputtering yield has been developed. The indium sputtering by Bim + (m = 1-7) cluster ions with energy 2-10 keV has been studied. A non-additive increase in the total sputtering yield with the raise in the number of atoms in cluster projectiles has been found. Copyright © 2012 John Wiley & Sons, Ltd. Copyright © 2012 John Wiley & Sons, Ltd.

Kosimov D.P.,University of Antwerp | Dzhurakhalov A.A.,University of Antwerp | Dzhurakhalov A.A.,Arifov Institute of Electronics | Peeters F.M.,University of Antwerp
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

The lowest-energy configurations of Cn (n≤55) clusters are obtained using the energy-minimization technique with the conjugate gradient method where a modified Brenner potential is invoked to describe the carbon and hydrocarbon interaction. We found that the ground-state configuration consists of a single ring for small number of C atoms and multiring structures are found with increasing n, which can be in planar, bowl-like or caplike form. Contrary to previous predictions, the binding energy Eb does not show even-odd oscillations and only small jumps are found in the Eb (n) curve as a consequence of specific types of edges or equivalently the number of secondary atoms. We found that hydrogenation of the edge atoms may change the ground-state configuration of the nanocluster. In both cases we determined the magic clusters. Special attention is paid to trigonal and hexagonal shaped carbon clusters and to clusters having a graphenelike configuration. Trigonal clusters are never the ground state while hexagonal-shaped clusters are only the ground state when they have zigzag edges. © 2010 The American Physical Society.

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