# Mechanisms of sequential particle transfer and characteristics of light neutron-excess and oriented nuclei

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## Abstract

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 ^{6}He, ^{10}Be, ^{12}B (both in dineutron and cigarlike configurations) is restored by analyzing the differential cross sections of elastic alpha-6He-scattering and ^{9}Be(*d*, *p*)^{10}Be and ^{10}B(*t, p*)^{12}B 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 ^{6}He both configurations contribute to a two-neutron halo, while in ^{10}Be there is a barely noticeable one-neutron halo, and in ^{12}B 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.

## Keywords

Differential Cross Section Spectroscopic Factor Step Mechanism Virtual Cluster Neutron Halo## Preview

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