Polarization observablesΣ,P y,T 1 in the reaction\vec \gamma d \to \vec pn at photon energies between 200 and 600 MeV and dibaryon resonances

The polarization observables Σ,P _y ,T ₁,P _y ^⊥ ,P _y ^∥ are derived in proton polarization measurements of the \(\vec \gamma d \to \vec pn\) reaction, using a linearly polarized photon beam of energies between 300 and 600 MeV for c.m.s. proton emission angles of 90° and 120°. A multipole analysis is performed in the framework of the gauge-invariant pole model considering theγN→πN amplitudes and the deuteron structure without dibaryon resonances and with different sets of isovector and isoscalar dibaryon resonances. It is shown that the inclusion of dibaryon resonances substantially improves agreement with experimental data.     

New allotropic forms of carbon based on С<Subscript>60</Subscript> and С<Subscript>20</Subscript> fullerenes with specific mechanical characteristics

New allotropic forms of carbon based on С₆₀ and С₂₀ fullerenes are considered. The most stable carbon compounds are found using an evolution algorithm, and their crystal structure (X-ray diffraction spectra) and electron (band structure) and mechanical (moduli of elasticity, hardness) characteristics are studied. The carbon phase with the tetragonal symmetry with mechanical properties close to those of a diamond crystal and having a narrow band gap is found.     

Origin of Porous Silicon Photoluminescence Peaks in the Wavelength Range 460–700 nm

The change in the photoluminescence peaks of porous silicon at λ = 640–670 and 540–560 nm at 300 and 77 K, as well as their behavior after low-temperature annealing of the samples at 500°С, has been studied. The change in these peaks correlated with that in the IR spectra. The peak at 640–670 nm has been explained by the existence Si–OH groups on the porous silicon layers and the peak at 540–560 nm, by the photoluminescence of the silicon matrix per se.     

Anisotropy of Ionic Conductivity of TbF3 Crystals

Crystallography Reports - Temperature measurements (in the range of 375–830 K) of the ionic conductivity of terbium trifluoride single crystals (structure type β-YF3) along three...     

Ordering of tysonite structure in an as-grown Er0.715Ca0.285F2.715 crystal and in a component of annealed two-phase crystal of the Er0.67Ca0.33F2.67 composition

The structures of the as-grown tysonite phase (TP) Er_0.715Ca_0.285F_2.715 as grown and the tysonite component in a crystal of the Er0.67Ca0.33F2.67 composition annealed at 760°C have been determined by X-ray diffraction methods from the main reflections in the sp. gr. P6₃/mmc, Z = 2. Ca²⁺ cations in the Er_0.715Ca_0.285F_2.715 structure occupy the 2c site on the 6₃ axis, thus confirming the conclusion about the symmetrizing effect of alkaline earth cation, which was made previously for the Y_0.715Ca_0.285F_2.715 compound. Er³⁺ cations are disordered over 6h sites around this axis. The Er_0.67Ca_0.33F_2.67 composition contains Er_0.67+δCa_0.33?δF_2.67+δ TP and inclusions of distorted fluorite phase rhβ-Ca₈Er₅F₃₁. The tysonite and two fluorite lattices have no “correct” relationship. Ca²⁺ cations and a half of TP Er³⁺ cations are fixed in the 2c sites, while the other Er³⁺ cations are disordered over the 6h sites. Superstructural ordering occurs in Er_0.715Ca_0.285F_2.715 crystals; however, the process is not completed, as follows from the character of the diffraction pattern. Weak satellite reflections in the diffraction pattern of the Er_0.67Ca_0.33F_2.67 composition are indicative of the development of TP ordering processes but remain unfit for structural calculations.     

New Investigations of the Crystal Structure of Lead Germanate Pb5Ge3O11

Crystallography Reports - Perfect stoichiometric Pb5Ge3O11 single crystals have been synthesized by the flux method. Their cationic and anionic stoichiometry is confirmed by chemical analysis. The...     

CH3NH3PbBr3 Nanocrystals Formed in situ in Polystyrene Used for Increasing the Color Rendering Index of White Leds

Theoretical and Experimental Chemistry - A new method is proposed for the formation of MAPbBr3 nanoparticles in situ in a dispersion of polystyrene in toluene in the absence (MAPbBr3@PS) and...     

Microstructure of Si Crystals Subjected to Irradiation with High-Energy H+ Ions and Heat Treatment by High-Resolution Three-Crystal X-Ray Diffraction and Transmission Electron Microscopy

Physics of the Solid State - The structural features of the formation of radiation defects in proton-implanted layers of silicon plates during their heat treatment have been studied. New data on...     

The Intrinsic Fluorine-Ion Conductivity of Crystalline Matrices of Fluoride Superionics: BaF2 (Fluorite Type) and LaF3 (Tysonite Type)

Physics of the Solid State - The intrinsic fluorine-ion conductivity σlat of BaF2 (CaF2 fluorite type) and LaF3 (tysonite type) crystals is studied by the impedance spectroscopy method. These...