Inelastic deformation of C60 single crystals in the temperature range 80–300 K

The rate spectrum of small inelastic strains of the C₆₀ single crystal in the temperature range 80–300 K has been obtained with a precision laser interferometer. It is revealed that the spectrum exhibits two large peaks in the glass formation (90–100 K) and phase transition (250–260 K) ranges. A small strain acceleration is also observed at ～220 and 240 K. The first two maxima are attributed to the changes in strain resistance upon transitions, and the strain acceleration at 220 and 240 K is associated with the annealing of the defects formed upon rapid cooling of the crystal. It is demonstrated that the peak at 250–260 K broadens with an increase in the stress. The spectrum of strain rates is compared with the calorimetric curve for the same single crystal.     

Pseudoelasticity of the Ti-Ni alloy subjected to omnidirectional pressure

Under certain (not just any) conditions, omnidirectional pressure applied to the Ti-Ni alloy is shown to change its superelastic properties, similar to the application of deforming force.     

Optical properties of InAs quantum dots in a Si matrix

We report on the optical properties of nanoscale InAs quantum dots in a Si matrix. At a growth temperature of 400°C, the deposition of 7 ML InAs leads to the formation of coherent islands with dimensions in the 2–4 nm range with a high sheet density. Samples with such InAs quantum dots show a luminescence band in the 1.3 μm region for temperatures up to 170 K. The PL shows a pronounced blue shift with increasing excitation density and decays with a time constant of 440 ns. The optical properties suggest an indirect type II transition for the InAs/Si quantum dots. The electronic structure of InAs/Si QDs is discussed in view of available band offset information.     

Small-inelastic-strain rate spectrum of C60 single crystals near the phase transition at 250–260 K

The temperature spectrum of small-inelastic-strain rates in a vapor-phase-grown C₆₀ single crystal has been measured within the 200–290 K interval with a high-precision strain-rate meter based on a laser interferometer. The spectrum exhibits a strong peak in the region of the phase transition at 250–260 K and a slight strain acceleration at ∼240 K, which correlates well with the calorimetric curve. The first maximum is associated with strain that developes more easily in an fcc than in a primitive cubic lattice, and the second, to the effect on the strain rate of annealing of the defects created with fast crystal heating. Fiz. Tverd. Tela (St. Petersburg) 41, 1115–1118 (June 1999)     

Antiferromagnetism in hydrated 123 compounds

Copper nuclear quadrupole resonance and zero-field nuclear magnetic resonance (ZFNMR) studies of YBa₂Cu₃O_6.5 show that a magnetic phase appears in underdoped 123 superconductors treated in ambient moist air. The studies give convincing evidence that the “empty” CuO chains play the role of easy water insertion channels. The reaction occurs first in ordered regions of the crystallites. The final product of the reaction is a nonsuperconducting antiferromagnetic compound characterized by at least two types of magnetically ordered copper ions, with ZFNMR spectra in the frequency ranges 46–96 and 96–135 MHz, respectively. Even for powder samples fixed in an epoxy resin, this reaction is found to have partially occurred after a few years. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 10, 739–744 (25 May 1999) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Morphology and Temperature Phase Transitions in α,ω-Alkanediols with Different Chain Lengths

A comparative analysis of phase transitions in diols with various chain lengths [(CH₂)₄₄(OH)₂ and (CH₂)₂₂(OH)₂] and changes in their absorption spectra with temperature have been investigated by DSC and FTIR. Analysis of the DSC data has led to the conclusion that the low-temperature phase transition of (CH₂)₂₂(OH)₂ in a solid state (T_s-s = 367.1 K) is a phase transition of the first order, while the high-temperature phase transition (T_m = 376.3 K) is of the second order, i.e., a transition of the order-disorder type. Splitting of the IR absorption bands into doublets at 720-730 cm⁻¹ and 1463-1473 cm⁻¹ indicates that crystalline subcells in the lamellae of both diols are orthorhombic lattices with the parameters typical of hydrocarbons. IR spectra showed that at the phase transition temperature T_s-s transformation of an orthorhombic subcell into a hexagonal one occurs. This type of molecular chain packing remains the same up to the melting temperature T_m. In a (CH₂)₄₄(OH)₂ diol, the ortho-hexagonal subcell transition occurs only at the melting temperature (390.0 K). The wide IR band in the region from 3000 cm⁻¹ to 3600 cm⁻¹ shows that end hydroxyl groups of diol molecules form, on the surfaces of lamellar crystals, long (polymer) regular sequences consisting of intermolecular hydrogen bonds.     

Gammas and Charged Particles Identification in Lateral and Additional Apertures of GAMMA-400

Physics of Atomic Nuclei - The GAMMA-400 (Gamma Astronomical Multifunctional Modular Apparatus) will be a new generation satellite gamma-observatory. The gamma-ray telescope GAMMA-400 consists of...     

Comparative analysis of TXRF-spectroscopy efficiency under the testing target excitation by fluxes formed by the slit-cut system and waveguide-resonator

The results of the comparative study of the Ba_1.4Y_1.0Cu_2.4O_7.0/SrTiO₃ epitaxial structure by the TXRF method under conditions of the exciting flux formation by a slit-cut system and a planar x-ray waveguide resonator (PXWR) with a specific design are presented. Experimental measurements were performed on a TXRF-model spectrometer built on the base of an HZG-4 precision digital goniometer. The spectrometer setup supplied the immutability of the x-ray optical scheme upon changing the exciting flux former. As a result, we found conditions where the TXRF analysis of the testing target is more effective with the use of the PXWR exciting flux former.     

Formation of silver nanoparticles with dielectric shell on the silver-containing glass during laser evaporation and ablation

We demonstrate a new method of silver nanoparticles formation on a silver-containing glass surface due to its irradiation by a pulsed CO₂ and YAG:Nd lasers. The particles are formed as a result of reduction of silver ions from the glass at the edges of a laser torch emerging during evaporation and ablation. The settled particles are then fixed on sample surface by a shell of glass dielectric components. The method allows creating plasmonic nanostructures on the glass surface for sensing applications.     

A Piezoceramic Resonator for Sonoluminescence Analysis

Acoustical Physics - The results of the numerical simulation and experimental study of an entirely piezoceramic cylindrical resonator to generate sonoluminescence are presented. The data on the...