A study of certain complex compounds of iron with the aid of magnetic measurements and the method of nuclearγ-resonance

Russian Chemical Bulletin -     

Variation of γ-ray spectra with the energy of channeled electrons

The spectral dependence of the γ-radiation produced by channeled electrons of different energies, E = 600, 750 and 900 MeV in 0.35 mm thick diamond was measured with a NaI(Tl) photon spectrometer. The energy dependences of the basic spectral features of the channeling radiation were determined.     

On the electromagnetic radiation of channeled particles in a curved crystal

A simple model calculation of the channeling of charged particles in a curved crystal is presented. The characteristics of the powerful radiation from relativistic particles associated with the motion in a curved channel are discussed.     

Anomalous transmission of swift electrons in thick crystals

A large penetration of swift electrons along the lattice crystallographic axes was observed. The center transmission peak of 2 MeV electrons along the 〈100〉 axis in 110 μm NaCl shows a narrow dip of width at half-minimum (0.2 ± 0.05). The half-width of the maximum base (0.7 ± 0.1) is in agreement with the classical mechanical calculation.     

High-speed electronics of the T0 detector for the ALICE experiment (CERN)

The design and special features of the main units of high-speed electronics for the trigger subsystem of the T0 detector of the ALICE experiment are considered. Its characteristic time resolution is 50 ps. The dead time does not exceed 25 ns.     

Parametric x-ray radiation generated by 5.7-MeV electrons in a pyrolytic-graphite crystal

Parametric x-ray radiation is observed in a mosaic pyrolytic-graphite crystal irradiated with a 5.7-MeV electron beam. The first-order (002) reflection of parametric x-ray radiation is detected in Bragg geometry. In the measured spectra, there is a peak at about 8 keV. The detector used is arranged at an angle of Θ_D=2Θ_B=27° with respect to the electron beam, where Θ_B is the Bragg angle. The target thickness is 0.3 mm. The spectra of parametric x-ray radiation are measured at various angles of target orientation with respect to the axis of the incident-electron beam.     

Catalytic properties of Ce<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Zr<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>2</Subscript> prepared using a template in the oxidation of CO

The catalytic activity in CO oxidation of Ce _x Zr_1–x O₂ double oxides prepared using pine sawdust and cetyltrimethylammonium bromide (CTAB) as templates is compared. It is found by means of SEM and the low-temperature adsorption of N₂ that biomorphic oxides reproduce the macropore structure of the template. It is shown via XRD and Raman spectroscopy that all samples contained mixed ceria-zirconia oxide. The double oxides form a cubic phase with a lattice of the fluorite type at a ratio of Ce: Zr = 4, regardless of the nature of the template; when Ce: Zr = 1, the biomorphic mixed oxide forms a tetragonal phase. According to Raman spectroscopy and XRD it was shown that the distortion of the oxygen sublattice is higher in biomorphic samples. Energy dispersive analysis shows that Ca impurities were present in the biomorphic samples, introducing additional distortions in the lattice of double oxide and leading to the formation of anionic vacancies. It is found that when Ce: Zr = 4, the conversion of CO on biomorphic oxide in the range of 100–350°C is higher than that observed for Ce _x Zr_1–x O₂ (CTAB); reducing the Ce: Zr ratio in the biomorphic sample to 1 results in a marked decrease in CO conversion at 100–200°C. It is concluded that these differences are due to changes in the mobility of the lattice oxygen.     

Observation of coherent X-ray production by 800-MeV electrons in a periodic triple-crystal target

The production of coherent x radiation by 800-MeV electrons in a target consisting of three 16-μm silicon crystals is investigated at the Tomsk synchrotron. The target structure makes it possible to observe from each crystal in turn, as the target is rotated, the radiation due to the summation of parametric x radiation (PXR) and the diffracted resonance transition radiation (DRTR) produced at the surfaces of the preceding crystals. The orientational dependence obtained shows that the contribution of the DRTR increases with the number of the crystal in the series, so that the angular density of the DRTR from the third crystal is approximately 1.7 times higher than the density of the PXR. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 8, 594–599 (25 April 1997)     

Temperature dependence of anomalous Rutherford scattering of fast electrons in crystals

In contrast to the channeling of positively charged particles, the effect of the crystal temperature on orientational scattering of fast electrons has not been investigated up to now. Only in [1] did they observe a decrease in the efficiency of the inverse scattering of ^–-particles upon the heating of <100> KCl and KBr crystals, which they explained by a decrease in the efficiency of focusing of the electrons on chains of atoms. In this article the effect of thermal vibrations of atoms on the interaction of electrons with single crystals is discussed within the framework of the model of bound states of fast electrons with atomic arrays and crystal planes, which consistently explains both the high penetration of particles into the lattice and the anomalous Rutherford scattering under channeling conditions [2, 3]. Detailed discussion is carried out for <111> and (100) Si crystals and electron energy E=(1.0–1.5) MeV.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 29–35, July, 1978.