Forward-angle yields of 2≤Z≤11 isotopes in the reaction of 18O(35A MeV) with 9Be

A systematic investigation of the forward-angle inclusive yields of 2≤Z≤11 isotopes produced in collisions of ¹⁸O projectile nuclei with a ⁹Be target in the Fermi energy region (35A MeV) is performed. The measurements were based on the use of the COMBAS double achromatic kinematical separator in the spectrometry mode at the Flerov Laboratory of Nuclear Reactions at the Joint Institute for Nuclear Research, FLNR (JINR, Dubna). The velocity, isotopic, and element distributions are presented. There is no unique mechanism that would explain the total set of results obtained in this experiment. A dominant role of low-energy reaction mechanisms is observed. The intensity of secondary beams of halolike nuclei ¹¹Li, ¹²Be, and ¹⁴Be is determined.     

Aspects of alpha-particle scattering and structure of the nuclear surface

The interaction of α particles above 5 MeV with a 2s-1d target is dominated by resonances. It cannot be described only in terms of a mean-field one-body potential. An analysis of the elastic α-particle scattering by ²⁸Si encourages the comprehension of the resonance states to be mainly fragments of a mixed-parity band. In the present article, the angular distributions of particles scattered by ³²S are analyzed in terms of such bands. The analysis of new data from an experiment made at Florida State University reveals the existence of states that do not belong to the above bands. This follows from a coupled-channel analysis of the elastic and inelastic (2⁺) cross sections. An α-particle structure at the nuclear surface is suggested.     

Cyclic deformation of aluminium and its alloys

The formation of slip bands is the main mechanism of cyclic deformation in pure Al. Their density, orientation and heights in polycrystalline Al were investigated during cycling. Types, sizes and densities of precipitates are responsible for the mode of cyclic deformation in AlCu4 pure alloy. In technical Al alloys intermetallic phases have detrimental effects on deformation homogeneity and largely govern the fatigue mechanism of the material and especially microcrack initiation.     

含氧光敏引发体系的研究——Ⅵ.二苯酮/三乙胺体系引发光聚合过程中的再次引发效应

过去,作者曾发表了多种光敏引发体系引发烯类单体光聚合的工作,在研究2,2-二甲氧基苯乙酮在氧存在下引发甲基丙烯酸甲酯光聚合时,结合在聚合物链端的引发剂碎片具有光化学活性,在光聚合反应中产生高分子自由基,发生再次聚合,出现高分子量     

Reflections on spontaneous asymmetric synthesis by amplifying autocatalysis

Spontaneous generation of chirality was observed in the course of studying the mechanism of asymmetric autocatalysis by NMR in ZnR2 alkylation of pyrimidin-5-aldehydes. A systematic study was carried out in order to discover its origins. Even in clean fresh non-glass reaction vessels spontaneous ee was clearly observed, and was not dependent on any single reaction parameter. For comparison it was demonstrated that enantiomerically pure Zn alkoxide catalyst could control the configuration of the reaction product even when present at below micromolar concentrations. The high propensity of the Soai reaction system to produce an enantiomerically enriched product without initial bias is suggested to result from stochastic effects. These are especially important in autocatalysis because all the final products can be derived by breeding from a small number of initial events. The statistical excess of one enantiomer in that set is sufficient to generate a measurable ee in the product. The process is aided by the requirement for dimerisation before the product is an active catalyst. An enumeration that rationalises these observations is provided.     

Stepwise delivery of two methoxy groups of arylaldehyde acetals across the phenyl ring. Vacant site-controlled palladium catalysis

A new catalytic cyclization of o-alkynylbenzaldehyde acetals 1 to the functionalized indenes 2 was found to be strictly controlled by the number of triphenylphosphine ligands on the Pd catalyst. Only complexes with three available coordination sites on Pd catalyze this reaction. Mechanistic study suggests that pi-coordination of Pd to the benzene ring is a key step controlled by the number of vacant coordination sites.     

Calculation scheme of heavy-ion collisions within the framework of a modified hydrodinamic approach

A hydrodynamic approach to describing heavy-ion collisions with allowance for the emission of the secondary particles is developed. The compression, the expansion, and break-up stages of the resulting hotspot are considered. The formed shock wave has a time-dependent front. The calculated spectra of produced protons are compared with experimental data.     

Investigation of the properties of nuclei with extreme neutron excess in the vicinity of neutron magic numbers

Properties of even-even nuclei with extreme neutron excess in the vicinity of neutron magic numbers up to and beyond the neutron drip line (NDL) are calculated by the Hartree-Fock (HF) method using Skyrme forces (Ska, SkM*, Sly4, SkI2, SkP) with allowance for axial deformation and BCS-approximation pairing. It is shown that chains of isotones with the neutron numbers N = 32, 58, 82, 126, 184, and 258 beyond the NDL form peninsulas of nuclei stable with respect to emission of one neutron, and occasionally peninsulas of nuclei stable with respect to the emission of two neutrons. The length of these peninsulas in (N, Z) space depends on the choice of the Skyrme forces, while their locations are at the same N = 32, 58, 82, 126, 184, and 258 and do not depend on the choice of forces. The investigated isotones restore stability beyond the NDL due to the complete filling of subshells with high angular momentum and to the intrusion of corresponding neutron levels in the region of discrete bound states. The stability of the numerical solution to the HF equations for nuclei belonging to the peninsulas of stability is analyzed.     

Determining the statistical weight of multicluster wave functions for light nuclei in a parametrized phase analysis

The experimental angular distributions of light alpha-cluster nuclei are described. Based on fitting, we find that the experimental angular distribution splits into two diffraction modes: the first has a short oscillation period on the nucleus as a whole, and the second has long oscillation periods on the alpha-cluster substructures. Fitting also reveals that the cross sections rising above the Rutherford level for light nuclei is explained by the additivity (modulation) of the alpha-particle mode of elastic scattering (the scattering of alpha particles on alpha-particle clusters).     

On some regularities in multinucleon transfer reactions with heavy ions

Multinucleon transfer reactions have been investigated by bombarding ²³²Th and ¹⁹⁷Au targets with 137 MeV ¹⁶O ions. An exponential yield dependence on the Q-values was observed for nucleon exchange reactions.