Beryllium (boron) clustering quest in relativistic multifragmentation (BECQUEREL Project)

A physical program of irradiation of emulsions in beams of relativistic nuclei named the BECQUEREL Project is reviewed. It is destined to study in detail the processes of relativistic fragmentation of light radioactive and stable nuclei. The expected results would make it possible to answer some topical questions concerning the cluster structure of light nuclei. Owing to the best spatial resolution, the nuclear emulsions would enable one to obtain unique and evident results. The most important irradiations will be performed in the secondary beams of He, Be, B, C, and N radioactive nuclei formed on the basis of JINR Nuclotron beams of stable nuclei. We present results on the charged state topology of relativistic fragmentation of the ¹⁰B nucleus at low energy-momentum transfers as the first step of the research.     

Investigation of clustering in light nuclei by means of relativistic-multifragmentation processes

New results concerning the topology of the fragmentation of relativistic nuclei ⁷Li and ¹⁰B are presented. A program is proposed for studying the cluster structure of stable and radioactive nuclei. The use of emulsions in the investigation of nuclear clustering in the fragmentation of light nuclei at energies are in excess of 1 GeV per nucleon is discussed.     

The 23 K superconducting phase YPd2B2C

We have carried out a systematic structural, electric, and magnetic study on Y---Pd---B---C samples with different compositions with emphasis on the as-cast and annealed YPd₅B₃C_0.3 which was first reported to superconduct at 23 K by Cava et al. We found that the tetragonal body-centered YPd₂B₂C with lattice parameters a=3.71 Å and c=10.81 Å is the phase responsible for the 23 K superconductivity and that YPd₂B₂C is metastable, which is consistent with the suggestion made by Cava et al. [1]: it is not stable at high temperatures nor stabilizable by Ni doping, although its isostructural compound, YNi₂B₂C, exists. Two new phases with Y:Pd ratios of 1:7 and 2:3, respectively, have also bee detected.     

Full four‐component relativistic calculations of the one‐bond 77Se–13C spin‐spin coupling constants in the series of selenium heterocycles and their parent open‐chain selenides

Four‐component relativistic calculations of ⁷⁷Se–¹³C spin–spin coupling constants have been performed in the series of selenium heterocycles and their parent open‐chain selenides. It has been found that relativistic effects play an essential role in the selenium–carbon coupling mechanism and could result in a contribution of as much as 15–25% of the total values of the one‐bond selenium–carbon spin‐spin coupling constants. In the overall contribution of the relativistic effects to the total values of ¹J(Se,C), the scalar relativistic corrections (negative in sign) by far dominate over the spin‐orbit ones (positive in sign), the latter being of less than 5%, as compared to the former (ca 20%). A combination of nonrelativistic second‐order polarization propagator approach (CC2) with the four‐component relativistic density functional theory scheme is recommended as a versatile tool for the calculation of ¹J(Se,C). Solvent effects in the values of ¹J(Se,C) calculated within the polarizable continuum model for the solvents with different dielectric constants (ε 2.2–78.4) are next to negligible decreasing negative ¹J(Se,C) in absolute value by only about 1 Hz. The use of the locally dense basis set approach applied herewith for the calculation of ⁷⁷Se–¹³C spin‐spin coupling constants is fully justified resulting in a dramatic decrease in computational cost with only 0.1–0.2‐Hz loss of accuracy. Copyright © 2014 John Wiley & Sons, Ltd.     

Effect of electron irradiation on the structure and mechanical properties of 36% Ni, 12% Cr, 3% Ti, 1% Al age-hardened austenitic steel subjected to various modes of thermomechanical treatment

The effect of electron irradiation on the structure and mechanical properties of 36% Ni, 12% Cr, 3% Ti, 1% Al age-hardened austenitic steel after different modes of thermomechanical treatment, including quenching, rolling with a 99% degree of compression, and aging, is studied experimentally in the constant current mode with a fluence of 10¹⁹ freq cm^?2. Regularities of the changes in the structural phase composition and mechanical properties of the investigated alloy are established as a result of electron irradiation. Scientifically grounded recommendations are given for selecting modes of thermomechanical treatment, supplemented by irradiation and ensuring the optimum combination of strength and ductility in 36% Ni, 12% Cr, 3% Ti, 1% Al age-hardened austenitic steel.     

New Luminescent Lanthanide Tetrakis-Complexes NEt4[LnL4] Based on Dimethyl-N-Benzoylamidophosphate

New lanthanide dimethyl-N-benzoylamidophosphate (HL) based tetrakis-complexes NEt₄[LnL₄] (Ln³⁺=La, Nd, Sm, Eu, Gd, Tb, Dy) are reported. The complexes are characterized by means of NMR, IR, absorption, and luminescent spectroscopy as well as by elemental, X-Ray, and thermal gravimetric analyses. The phenyl groups of the four ligands of the complex anion are directed towards one side, while the methoxy groups are directed in the opposite side, which makes the complexes under consideration structurally similar to calixarenes. The effect of changing the alkali metal counterion to the organic cation NEt₄⁺ on the structure and properties of the tetrakis-complex [LnL4]^- is analyzed. The complexes exhibit bright characteristic for respective lanthanides luminescence. Rather high intensity of the band of ⁵D₀→⁷F₄ transition, observed in the luminescence spectrum of NEt₄[EuL₄], is discussed based on theoretical calculations.     

Charge topology of the coherent dissociation of relativistic <Superscript>11</Superscript>C and <Superscript>12</Superscript>N nuclei

The charge topology of coherent-dissociation events is presented for ¹¹С and ¹²N nuclei of energy 1.2 GeV per nucleon bombarding nuclear track emulsions. This topology is compared with respective data for ⁷Be, ^8,10B, ^9,10C, and ¹⁴N nuclei.     

Electromagnetic dissociation of relativistic 8B nuclei in nuclear track emulsion

Experimental data on fragmentation channels in peripheral interactions of ⁸B nuclei in nuclear track emulsions are presented. A detailed analysis made it possible to justify selections of events of the electromagnetic-dissociation process ⁸B → ⁷Be + p and to estimate its cross section. Events of ¹⁰C peripheral dissociation that were observed in the same exposure are described.     

Peripheral fragmentation of 8B nuclei in nuclear emulsion at an energy of 1.2 GeV per nucleon

The results obtained by studying the charge topology of fragments produced in the peripheral dissociation of relativistic ⁸B nuclei in emulsion are presented. Fifty-five events of the peripheral dissociation of a ⁸B nucleus in events where there was no production of target-nucleus fragments and mesons (“white stars”) were selected. A leading contribution of the ⁸B → ⁷Be + p mode, which has the lowest energy threshold, was revealed on the basis of these events. Information about the branching ratios for dissociation modes characterized by a higher multiplicity was obtained. The dissociation of the ⁷Be core in ⁸B bears resemblance to the dissociation of a free ⁷Be nucleus. The transverse-momentum distributions of fragments originating from the ⁸B → ⁷Be + p dissociation mode were obtained. For these distributions, a small mean value of 〈P*_T〉 = 52 ± 5 MeV/c in the c.m. frame suggests a low binding energy of the outer proton in the ⁸B nucleus. An indication of a strong azimuthal correlation of the fragments ⁷Be and p was found.     

Exposure of nuclear track emulsion to 8He nuclei at the ACCULINNA separator

Nuclear track emulsion is exposed to a beam of radioactive ⁸He nuclei with an energy of 60 MeV and enrichment of about 80% at the ACCULINNA separator. Measurements of 278 decays of the ⁸He nuclei stopped in the emulsion allow the potential of the α spectrometry to be estimated and the thermal drift of ⁸He atoms in matter to be observed for the first time.