Vol 11, No 3 (2017)

The effect of Ne ion beam etching on the roughness of materials for optical substrates—fused silica and beryllium—is studied. It is shown that the treatment of a fused silica surface by neutralized Ne ions with an energy of 400–800 eV makes it possible to smooth roughnessed in the range of higher spatial frequencies of 3–63 μm^–1 at an incidence angle of 0°–30°. For beryllium, the possibility of smoothing the surface roughness at an ion energy of 400 eV is found.

The paper presents a brief review of the possible applications of cluster beams for emission in the short-wavelength region for the treatment of ultrasmooth surfaces and the fabrication of nanostructures. An experimental device which is under development is described in brief, and its calculated characteristics are presented. The issues that can be resolved by means of this device are outlined.

The possibility of interactively controlling the surface curvature of a single-crystal Si(100) plate used as a diffraction element is investigated. The initial component-surface profile is specified by the substrate shape, parameters of the adhesive, and the temperature of its adhesion to the substrate. The results of calculating the changes in surface profile and its curvature radius are presented.

The features of the electronic structure of Yb4d, N1s, C1s, O1s, Br3d core levels and the valence band of ytterbium metalloporphyrins Yb(acac)TPPBr8, Yb(acac)TPP, TPPBr8, and TPP are studied by photoelectron spectroscopy. The position and structure of the Yb4f level for Yb(acac)TPPBr8 are determined by resonant photoemission at the BESSY-II synchrotron center. Simulations of the electronic structure of the valence band show good agreement between the calculated and experimental data. The change in the electronic structure of porphyrins during implantation of the central atom of ytterbium, namely, a more uniform redistribution of the electron density between nitrogen atoms of pyrrole and aza groups, is revealed. The photoelectron spectra of Yb4d states demonstrate the trivalent metal state (Yb³⁺) in rare-earth metalloporphyrins. The partial destruction of bromine ytterbium tetraphenylporphyrin compound as a result of thermal action is demonstrated.

The effect of thermal cycling on the appearance of alternating stresses in the walls of tubes of perlite low-alloyed and austenitic chromium–nickel steels is studied by X-ray diffraction to develop the criteria of their compatibility. Optimal operating temperatures are estimated for the basic metals and the weld seam realized on their basis. Coincidence between experimental estimates and optimal temperatures established under long-term operation is noted. This may be considered as confirmation of the possibility of applying the stated approaches in predicting the development of hot cracks in the zone of a weld seam and the selection of operating temperatures, at which fields of internal stresses of certain value and sign are formed.

The work presents data on the microhardness, average grain size, lattice parameters, and phase composition of Cu₅₇Be₄₃ metal alloy, annealed at a temperature of ~350°С for 1 h in a constant magnetic field with the intensity ranging from 80.0 to 557.0 kA/m. The main observed regularities of changes in the structure and properties of the material during annealing in a constant magnetic field and without it are formulated.

The findings of an investigation into the impact of ions on the atomic state of the upper layer of He‒Ne laser cathodes are presented. The research results are obtained using electron-probe microscopy, X-Ray photoelectron spectroscopy, and Auger spectroscopy, including the scanning mode. Changes in the surface compositions of the cathodes and active-element mirrors of lasers are revealed before and after tests.

A correction to the Bohr formula making it possible to explain the difference between the stopping powers of positively and negatively charged particles (the Barkas effect) is obtained in the quasiclassical approximation taking into account the difference between electron motion in a hydrogen atom as a function of the charge sign of the moving particle. The influence on the atomic electron of the moving particle leads to a change in the contribution of the adiabatic interaction, in the case of which the energy is not transferred in the majority of collisions, which is the reason for a decrease in the energy losses of slow particles compared with Bohr theory. The results of calculations show that the energy losses per path length unit can be represented in the form of the product of two functions, namely, the energy loss function (in accordance with Bohr theory) and the dynamic function taking into account corrections related to correction of the electron position in the target atom during the collision. Calculations carried out within the framework of classical dynamics make it possible to qualitatively estimate differences between the interaction of protons and antiprotons with target material atoms.

Computer methods whereby the inverse vibronic problem is solved on the basis of resonance fluorescence spectra with the use of modern quantum-mechanical methods for constructing structuraldynamic models of polyatomic molecules are discussed. An algorithm is proposed for solving the inverse vibronic problem according to resonance fluorescence spectra under laser excitation, and the corresponding calculation programs are constructed. The initial program data are acquired by means of an original software package which implements the scaling of quantum-mechanical force fields in two electronic states. The Duschinsky matrix and the initial matrix of shifts in normal coordinates caused by electron excitation are calculated in the Cartesian and natural vibrational coordinates. The program data are taken from quantum-molecular models based on calculations performed via ab initio modern quantum-mechanical methods and density functional theory. The algorithm is tested through the calculation of a model molecular system.

The internal structure of copper coins—a Golden Horde pulo of the 14th century AD and an ancient coin found in Phanagoria at sites of the 5–4th centuries BC—are studied by neutron tomography method. From a set of angular projections of neutron absorption, three-dimensional models of the analyzed objects are reconstructed and the analysis of their physical state is performed. In the copper pulo, a region characterized by a greater neutron beam attenuation coefficient is found. It is assumed that this region was formed due to the gradual penetration of patina into the coin. The neutron tomography data also make it possible to analyze the remnants of an antique coin found in underwater archeological studies. Areas of surface damage and cracks in the antique coin are shown, visually separated from the corrosion layer.

A model of the glow discharge cathode sheath in a mixture of argon with mercury vapor used in gas discharge illuminating lamps is developed. It takes into account that at the stage of lamp ignition the mercury atom density is by several orders lower than the argon atom density and depends on the temperature. The cathode sheath characteristics are calculated and it is shown that at a temperature increase, due to growing contribution of the mercury atom Penning ionization, the discharge cathode voltage drop is decreased and the ratio of the mercury and argon ion current densities at the cathode is increased. The energy spectra of the mixture component ion flows bombarding the cathode surface, as well as their corresponding effective sputtering rates and the sputtered atom flow densities, are found. It is shown that at low values of the discharge current density mercury ions practically do not participate in the cathode sputtering because their energies are less than the threshold sputtering energy. However, at its higher values they can make a significant contribution to the sputtering despite the small mercury content in the mixture.

Ferritic-martensitic steels alloyed with Cr and Ni are promising structural materials for the nuclear and thermonuclear power industry. Under the influence of neutron irradiation degradation of the plastic properties of these materials takes place as a result of the generation of extended defects such as dislocation loops, and the formation of new phases (precipitates). In this work the atomistic computer simulation of thermodynamic processes of the precipitation of alloying elements is carried out using the newest model of ternary Fe–Ni–Cr bcc (body-centered cubic) alloys and the Metropolis Monte Carlo method in combination with the method of classical Molecular Dynamics. The composition and microstructure of Cr–Ni clusters formed in defect-free alloys and alloys containing dislocation loops, depending on the temperature and concentrations of Ni and Cr, are studied. An increase in the Ni solubility limit in the presence of dislocation loops by 100–200 K, depending on the Ni concentration, is detected. The synergetic effect of Ni and Cr segregation near dislocation loops in ternary alloy is established: the presence of Ni weakens Cr segregation, whereas Cr can either attenuate or amplify Ni segregation depending on the concentration of Ni in the alloy, the temperature and the type (Burgers vector) of loop. In general, in ternary Fe–Cr–Ni alloys, the total segregation effect is less pronounced than in binary Fe–Ni and Fe–Cr alloys.

The modification of the (111) face of synthetic diamond under high-fluence (≥10¹⁸ ion/cm²) 30-keV Ar⁺ irradiation is studied experimentally. It is found that ion irradiation at room temperature results in the formation of a low-conductivity surface layer. Heat treatment when the target temperature is increased to 400°C results in a more than ten-fold exponential drop in the layer resistance, as compared to its value at room temperature. If the temperature of the irradiated diamond is increased from 30 to 400°C the layer resistance of the ion-induced conductive layer drops by more than two orders of magnitude to the level corresponding to the conductivity of graphite-like materials. The Raman spectra of the ion-induced conductive surface layer reflect the processes of structural disorder—sp²-carbon ordering and strong changes in the optical transmittance of diamond after ion irradiation.

The ultrasmall- and wide-angle neutron diffraction methods are used to study multiscale structures and phase transformations in synthetic opals at different temperatures and pressures (as high as 1500°C and 10 GPa, respectively). Monodisperse colloidal particles of amorphous silica dioxide (a-SiO₂) with an average diameter of 150‒1700 nm whose deviation from the mean is less than 5% are synthesized to fabricate the samples. Opal matrices up to 3 cm thick are obtained via the natural sedimentation of a SiO₂-globule suspension followed by drying and heat treatment. Neutron-diffraction processes are investigated using a DISK multidetector superposition diffractometer mounted at the IR-8 reactor of the National Research Centre Kurchatov Institute at a neutron wavelength of 1.668 Å. Ultrasmall-angle diffraction experiments are performed in the two-crystal mode of a STOIK spectrometer.

The motion of channeled particles in a single crystal is determined by the continuous potential of the crystallographic axes. The transverse motion of particles in the axial channeling mode is characterized by a discrete energy spectrum. In this paper, the criteria for selection of the continuous potential and the conditions for quantization of the transverse energy for axially channeled particles are discussed, and the criterion for the resonance capture of particles in the axial channeling mode during particle entrance into a single crystal is formulated; it requires that the particle’s angular momentum with respect to the channel axis coincides with a quantity that is a multiple of Planck’s constant. The effect of resonance capture can be observed, for example, via an increase in the intensity of electromagnetic radiation of the beam of channeled particles in the optical range at frequencies corresponding to transitions between the allowed levels of transverse motion.

The first results of an experimental investigation into the generation of X-ray bremsstrahlung under grazing interaction between the internal 18-MeV electron beam of a B-18 betatron and a silicon crystal 50 μm thick and 4 mm long along the electron beam are presented. The experiments refer to the research of X-ray formation in the case of the grazing interaction of electrons with layered structures created on thin Si substrate surfaces. In the case of emission from layered structures, radiation emitted from the substrates is an intense background varying greatly with substrate orientation. This must be taken into account when the orientation dependences of the characteristics, e.g., radiation formed in X-ray mirrors and waveguides, are measured.

The interaction between an atom located inside a crystal structure and a moving external particle is accompanied by changes in its environment, and as a consequence, the atom is additionally affected by it. The force impact of the image of a moving multiply charged ion on the state of an ultrathin carbon film is calculated. The p possibility of forming a pore in the film as a result of ion propagation through the film is shown. The size of the pore turns out to be strictly correlated with that of the ion wave packet incident from free space on the thin-film carbon crystal structure. It is possible to trace the formation of the boundary with a classically inaccessible region called the caustic surface by numerically solving the three-dimensional nonstationary Schrödinger equation in the problem of the collision between a moving multiply charged ion and a carbon atom. On the whole, the performed calculation confirms the previously obtained results.

The influence of mechanical force action combined with shear deformation implemented via Bridgman anvils on the dielectric properties of synthesized Pb(Zr_0.58Ti_0.42)O₃ powder is studied. It is ascertained that the physical properties of sintered ceramics can be controlled over a wide range upon varying the concentration and type of structural defects arising from the mechanical activation of powders.