Elementary processes during collisions of ions with tryptophan molecules

The relative cross sections of elementary processes occurring in single collisions of tryptophan molecules in the gaseous phase with He²⁺ ions with energy 4 keV/u are measured using time-of-flight mass spectrometry for studying the mechanism of radiation damage of amino acid molecules. The fragmentation channels for intermediate singly and doubly charged tryptophan molecular ions formed during one-electron capture, two-electron capture, and electron capture with ionization are investigated. Significant difference is observed in the mass spectra of fragmentation of intermediate doubly charged ions formed during the capture with ionization and double capture, which is associated with different energies of excitation of {C₁₁H₁₂N₂O₂}²⁺* ions.     

Dynamics of nanoparticle agglomeration in a magnetic fluid in a varying magnetic field

It is found that the dependence of the magnetic nanoparticle agglomerate length in a magnetic fluid on the applied magnetic field has three characteristic segments: a substantial increase in the agglomerate length with the magnetic field in the range of weak fields, a segment with an insignificant increase in the average length of agglomerates upon an increase in the field, and a sharp increase in the agglomerate length with a further increase in the field. It is shown that the agglomerate length increases in the range of strong magnetic fields due to a decrease in the spacing between adjacent agglomerates down to their complete coalescence. The total number of agglomerates decreases thereby.     

Possibility of adjusting photoluminescence spectra of Ca scheelites (CaMoO<Subscript>4</Subscript>: Eu<Superscript>3+</Superscript> and CaWO<Subscript>4</Subscript>: Eu<Superscript>3+</Superscript>) to the emission spectrum of incandescent lamps

The peculiarities of the photoluminescence of compounds CaMoO₄: Eu³⁺ and CaWO₄: Eu³⁺ with the scheelite structure associated with a change in the short- and long-range orders of the crystal lattice upon a change in the activator (Eu³⁺) of the photoluminescence range in the interval 1–4 mol %, in which the photoluminescence of the matrix is preserved in the range 484–557 nm, are investigated using X-ray phase analysis as well as photoluminescence, Raman, and diffuse reflection spectroscopies. The introduction of Eu³⁺ ions leads to the reconstruction of the lattice so that up to 10% of these ions stimulate the formation of centrosymmetric localization upon the substitution of Ca²⁺ ions in the noncentrosymmetric positions. It is found that the spectral radiant emittance of the more effective luminophore CaMoO₄: Eu³⁺ can be adjusted to this parameter for an incandescent lamp for the Eu³⁺ concentration of 1–2 mol %.     

Possibilities of structural engineering in multilayer vacuum-arc ZrN/CrN coatings by varying the nanolayer thickness and application of a bias potential

The possibility of attaining an superhard state in multilayer vacuum-arc ZrN/CrN coatings with a layer thickness of about 20 nm has been established. It has been shown that the application of a constant negative potential for structural engineering during deposition leads to the formation of solid solutions due to mixing of interfaces. The hardness of these systems exceeds 30 GPa. The application of a pulsed high-voltage bias potential at which the ordering of atoms stimulated by elevated mobility is observed makes it possible to suppress the mixing of the interfaces and to attain elevated hardness (up to 42 GPa) for nanometer layer thicknesses.     

Numerical simulation of the formation of compact strikers from low-sphericity linings

We consider the physicomathematical formulation of the problem of explosive formation of a penetrator from a low-sphericity copper lining. Calculations are made for the formation of a penetrator for a phlegmatized hexogen charge for two models of the behavior of the lining material (copper), and the results are compared with the experimental data.     

Thermal stability of the microstructure of 12% chromium ferritic–martensitic steels after long-term aging at high temperatures

The structure of EK-181 (RUSFER-EK-181, low-activation) and ChS-139 12% Cr ferritic–martensitic steels is investigated and their mechanical properties are tested after long-term (13500 h) aging at 450 and 620°C. The microstructure of the steels exhibits a high thermal stability, which provides the retention of their initial short-term mechanical properties at test temperatures.     

On the thermodynamics of turbulent convection

The thermodynamic properties of a steady-state flow in the gravitational field have been determined by applying the entropy production equation and the Prigogine theorem to an ideal one-component turbulent gas under the assumption that fluctuations are polytropic. Applications to the problems of the surface layer dynamics and free convection are also considered.     

Optical spectroscopy of intermetallic compounds TbNi<Subscript>2</Subscript>Mn<Subscript> <Emphasis Type="Italic">x</Emphasis> </Subscript> (<Emphasis Type="Italic">x</Emphasis> = 0, 0.5, 1)

The optical properties of intermetallic compounds TbNi₂Mn_x (x = 0, 0.5, 1) have been investigated using the ellipsometric method in the spectral range from 0.22 to 16 μm. The specific features of the modification of the dispersions of spectral characteristics with a variation in the manganese concentration have been determined. The behavior of the frequency dependences of the optical conductivity in the interband absorption region has been discussed in terms of the available data on the electronic structure of these compounds. The concentration dependences of a number of electronic parameters have been calculated.     

Influence of “ytterbium nanofilm–silicon Si(111)” interfaces on the valence of ytterbium

The work function of ytterbium films of nanometer thickness (from 1 to 16 monolayers) has been measured. The films have been prepared by sputtering of ytterbium in an ultrahigh vacuum on n- and p-type Si(111)7 × 7 silicon substrates with an electrical resistivity from 1 to 20 Ω cm. It has been shown that, in the films with a thickness of less than 8 monolayers, the work function depends nonmonotonically on the amount of ytterbium deposited on the surface (Friedel oscillations), whereas in the films with a thickness of more than 8 monolayers, the work function takes on a constant value (3.3 eV) that exceeds the work function for macroscopic samples (2.6 eV). This difference is associated with the fact that, during the formation of an Yb–Si interface, the large difference in the work functions of ytterbium and silicon (4.63 eV) leads to the transfer of a significant fraction of electrons from the metal to the semiconductor. This transfer of electrons from the film to silicon is accompanied by the lowering of the Yb 5d level below the Fermi level. As a result, the valence of the metal and, accordingly, the work function increase.     

Experimental investigation of the role of the triplet pairing in the superconducting spin-valve effect

An important role of the morphology of a superconducting layer in the superconducting spin-valve effect has been established. The triplet pairing induced by the superconductor/ferromagnet proximity effect has been experimentally investigated for samples CoO_x/Py1/Cu/Py2/Cu/Pb (where Py = Ni_0.81Fe_0.19) with a smooth superconducting layer. The optimization of the parameters of this structure has demonstrated a complete switching between the normal and superconducting states with a change in the relative orientation of magnetizations of the ferromagnetic layers from the antiparallel to orthogonal orientation. A pure triplet contribution has been observed for the sample with a permalloy layer thickness at which the superconducting spin-valve effect vanishes. A direct comparison of the experimental data with the theoretical calculation of the temperature of the transition to the superconducting state has been performed for the first time.