Towards a consistent understanding of the exotic nucleus Si28

[摘要] The issue of magicity of Si28 has been a contentious one. Fridmann et al., through studies of two-proton knockout reaction Si28 ⟶ Si28, presented strong evidence in support of magicity and sphericity of Si28. However in complete conflict with this, Bastin et al., gave equally strong empirical evidence, to show that the N = 28 magicity had completely collapsed in Si28 to make it well deformed. The consensus at present though is in favour of the validity of the latter experiment. However, our QCD based theoretical model supports the result of Fridmann experiment. They had explored the amazing persistence of the unique exotic nucleus Si28 as a stable structure within the nucleus Ca28; even after stripping off six-protons through the isotonic chain:Ca28 ⟶ Ar28 ⟶ S28 ⟶ Si28. Thus it is the novel and unexpected stability of proton shell closure at Z=14 in , which is playing such a dominant role in ensuring its magicity, while the neutron magic number N = 28, goes into hiding or actually disappears. Recently, SAA has shown that the fusion experiment of a beam of halo nucleus 6He with the target nucleus 238U , actually provided strong evidence that the “core” of the halo nucleus has the structure of a tennis-ball (bubble) like nucleus, with a “hole” at the centre of its density distribution. This provides us with clear-cut support for our Quantum Chromodynamics based model of clusters of tritons in neutron-rich nuclei. Here we show that our QCD based model, provides support to Fridmann et al. , showing that, Si28 has a spherically magic structure of 14H2 (14-tritons) with a tennis-ball (bubble) like structure with “hidden” N=28 neutrons.

[关键词] Exotic nuclei;New magicity;Halo nucleus;Tennis-ball nucleus;Bubble nucleus;Deformation;Sphericity;Triton;QCD;Quark model;Article