[en] The possibility of determining the momentum distribution of clusters in nuclei by using angular-correlation functions for particles originating from fragmentation reactions is considered. A set of independent kinematical variables is proposed, and conditions are formulated under which the angular-correlation function for final particles is proportional to the momentum distribution of clusters in a nucleus. It is found that the momentum distribution determined in this way represents a sensitive tool for determining the geometric parameters of the potential of intranuclear interaction

[en] The presence of two topologically different configurations, a dineutron and a cigar-like one, in the spatial wave function for the neutron-rich nucleus ⁶He is predicted. In elastic α⁶He scattering, the dineutron configuration leads to the appearance of backward maxima in the cross section for elastic α⁶He scattering. The cigar-like configuration is responsible for the scattering mechanism involving independent sequential neutron transfer and the formation of the ⁵He-⁵He virtual system. In order to estimate the contribution of this mechanism, the matrix element for the two-step sequential particle transfer is calculated by a method that takes into account delay in the interaction and which is realized in the QUADRO code. Calculations performed on this basis make it possible to estimate the weight of the cigar-like component in the wave function for the ⁶He nucleus

[en] The spatial structure of lithium isotopes is studied with the aid of the charge-exchange and (t, p) reactions on lithium nuclei. It is shown that an excited isobaric-analog state of ⁶Li (0⁺, 3.56MeV) has a halo structure formed by a proton and a neutron, that, in the ⁹Li nucleus, there is virtually no neutron halo, and that ¹¹Li is a Borromean nucleus formed by a ⁹Li core and a two-neutron halo manifesting itself in cigar-like and dineutron configurations

[en] On the basis of the shell model with an extended basis, the structure of "9Li-"9Be to "1"1Li-"1"1Be nuclei is examined with allowance for the competition of "j"j coupling and Majorana exchange forces via considering the sequential addition of neutrons, and the respective wave functions are determined. A formalism for calculating the spectroscopic factor for a dineutron and for individual neutrons in nuclei whose wave functions incorporate the mixing of shell configurations is developed. The reactions "9Li(t, p)"1"1Li and "9Be(t, p)"1"1Be treated with allowance for the mechanisms of dineutron stripping and a sequential transfer of two neutrons are considered as an indicator of the proposed structure of lithium and berylliumisotopes. The parameters of the optical potentials, the wave functions for the bound states of transferred particles, and the interaction potentials corresponding to them are determined from a comparison of the theoretical angular distribution of protons from the reaction "9Be(t, p)"1"1Be with its experimental counterpart. It is shown that a dineutron periphery of size about 6.4 fm is present in the "1"1Li nucleus and that a single-neutron periphery of size about 8 fm is present in the "1"1Be nucleus.

[en] The procedure for evaluating the second-order corrections to the matrix elements of the reaction A(x, y)B, which are obtained using the method of distorted waves with a finite radius of intercluster interaction (DWBAFR), is developed. It is based on the assumption of a virtual cluster structure of light nuclei and uses integral equations for a four-body problem in the Alt-Grassberger-Sandhas formalism. These corrections are related with the mechanisms of sequential particles transfer. The latter are represented by the quadrangle diagrams. Their matrix elements are summed up coherently with those given by the pole and triangle diagrams which were calculated by using DWBAFR. The computer code QUADRO is written for the numerical implementation of the method proposed. The statistical tensors of nucleus B formed in the reaction A(x, y)B at incident particle energies of about 10 MeV/nucleon in the center of mass frame are determined. Specific calculations allowed for description of both the experimental cross sections (0-rank statistical tensors) of various reactions (including those where nucleus B has some excess neutrons) and polarized characteristics of nucleus B* (in the case of the latter produced in the exited state). A two-neutron periphery of nuclei ⁶He, ¹⁰Be, ¹²B (both in dineutron and cigarlike configurations) is restored by analyzing the differential cross sections of elastic alpha-6He-scattering and ⁹Be(d, p)¹⁰Be and ¹⁰B(t, p)¹²B reactions. It is shown that the structure of neutron peripheries is fundamentally different for these nuclei and its feature depends on the way those neutron-excess nuclei are formed: in ⁶He both configurations contribute to a two-neutron halo, while in ¹⁰Be there is a barely noticeable one-neutron halo, and in ¹²B there is a “dineutron skin”. Orientation characteristics of nuclei B* are calculated. Their comparison with experimental data made it possible to draw important conclusions about a contribution to the statistical tensors of nucleus B* coming from the two-step mechanisms and its impact on the properties of oriented light nuclei, including their polarization. Finally, a simplified method for calculating the matrix elements of mechanisms, which take into account sequential particle transfer, is proposed. It is demonstrated to be correct by evaluating a contribution of the corresponding corrections to the total amplitude of the reaction.

[en] Within the theoretical formalism that combines a four-body problem with themultiparticle shell model, it is shown that the cross section for the dineuteron-stripping mechanism is consistent with the experimental angular distribution of protons from the ¹⁶O(t, p)¹⁸O reaction. This makes it possible to find the wave function for the relative motion of the dineutron and ¹⁶O and to obtain thereby the probability density W(r) for the dineutron in ¹⁸O, the nn–¹⁶O interaction potential, and the root-mean-square distance 〈L〉_nn between the dineutron and ¹⁶O. The respective calculations reveal that, at r ≈ 8 fm, the dineutron probability density and a rather deep nn–¹⁶O potential become negligible, which leads to the absence of a dineuntron periphery in ¹⁸O. It seems that one can explain this fact by a rather large value (12.19 MeV) of the dineutron binding energy in this nucleus. Thus, the ¹⁸O nucleus is quite compact an object, despite the excess of two neutrons, and has a neutron skin rather than a periphery.

[en] The cross sections for the (t, p) reactions on the lithium isotopes "9","1"1Li were calculated within a theoretical approach based on employing integral equations of the four-body problem in the Alt—Grassberger-Sandhas formalism and the multiparticle shell model. This made it possible to determine the wave functions for the relative motion of various clusters and the nuclear core and to calculate, on their basis, the root-mean-square radii of nuclei of the isotopes "9","1"1Li and the spatial structure of their neutron periphery. It is shown that the "9Li nucleus has virtually no neutron halo. The "1"1Li nucleus is a Borromean halo nucleus. The two-neutron periphery of this nucleus manifests itself in both spatial configurations, a dineutron and a cigar one, the respective root-mean-square radii being large (about 6.5 to 6.9 fm)

[en] Measured and calculated angular dependences of components of the polarization tensor of a ¹²C nucleus in the 2⁺ state at 4.44 MeV formed in various reactions involving light particles, as well as ²⁴Mg(2⁺, 1.369 MeV) and ²⁸Si(2⁺, 1.78 MeV) nuclei formed in inelastic alpha-particle scattering, are presented. The experimental tensor polarization in question was reconstructed on the basis of the densitymatrix spin-tensors found previously for these nuclei. The parameters of the quadrupole and hexadecapole orientation of the nuclei under study were obtained. The experimental polarization features were compared with the results of calculations based on the coupled-channel method. Special features of the behavior of tensor polarizations in various reactions were discussed. The similarity of the experimental angular dependences of the components of tensor polarizations in inelastic deuteron and ³He scattering on ¹²C nuclei, as well as in inelastic alpha-particle scattering on ²⁴Mg and ²⁸Si nuclei, was demonstrated.

[en] The contributions of various mechanisms to the production of the final nucleus ¹²C in the reaction ¹³C(³He, α)¹²C are estimated. These are neutron stripping and the transfer of the heavy cluster ⁹Be in the pole approximation or via a sequential transfer of virtual ⁸Be and a neutron. It is shown that the sequential mechanism of heavy-cluster transfer must be taken into account in order to describe correctly experimental data over the whole angular range

[en] The brief history of the development of investigations at the Skobeltsyn Institute of Nuclear Physics, Moscow State University (SINP MSU) in the field of space materials science is outlined. A generalized scheme of a numerical simulation of the radiation impact on spacecraft materials and elements of spacecraft equipment is examined. The results obtained by solving some of the most important problems that modern space materials science should address in studying nuclear processes, the interaction of charged particles with matter, particle detection, the protection from ionizing radiation, and the impact of particles on nanostructures and nanomaterials are presented.