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 Г_а. 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.