Specific features of capture reactions of real and virtual α-particles by 6Li and 7Li isotopes

Abstract

The article examines the features of the interaction of virtual and real α-particles with isotopes 6Li and 7Li with the formation of the ground and excited states of 10B and 11B nuclei. The multiparticle shell model is used to describe the structures of nuclei. The significant difference in the excitation spectra of 10B and 11B nuclei in the capture of real and virtual α-particles is explained by the structural features of these nuclei and different mechanisms of capture of α-particles. Real α-particles are captured in reactions (α, γ), and virtual ones - in lithium cluster transfer reactions. In both boron isotopes, the first decay channel is the α-particle, then there is an energy range of several MeV until the next decay channel with the emission of particles. Moreover, in this energy range, the S-factors are anomalously small. If the excited levels lie above the threshold for the breakup of the nucleus with the emission of certain particles a, then the S-factors turn out to be related to the partial widths of the decay Га. In contrast to spectroscopic factors, which do not depend on energy and are determined only by the structure of the initial and final states, the partial Γ-widths depend on the energy which the particles are emitted with. It is shown that, in a narrow energy range from the first threshold for the emission of particles to the second threshold, the cross sections for the excitation of residual nuclei by real and virtual α-particles differ significantly. Narrow beams of γ-quanta formed with large cross sections in reactions of radiative α-capture can be used for diagnostics of thermonuclear plasma.