Borromean structures in medium-heavy nuclei

Abstract

Borromean nuclear cluster structures are expected at the corresponding driplines. We locate the regions in the nuclear chart with the most promising constituents, it being protons and alpha-particles and investigate in details the properties of the possible borromean two-alpha systems in medium heavy nuclei. We find in all cases that the alpha-particles are located at the surface of the core-nucleus as dictated by Coulomb and centrifugal barriers. The two lowest three-body bound states resemble a slightly contracted ${}^8\text{Be}$ nucleus outside the core. The next two excited states have more complex structures but with strong components of linear configurations with the core in the middle. Alpha-removal cross sections would be enhanced with specific signatures for these two different types of structures. The even-even borromean two-alpha nucleus, ${}^{142}$Ba, is specifically investigated and predicted to have ${}^{134}\text{Te}-\alpha -\alpha$ structure in its ground state and low-lying spectrum.

Comments: 18 pages, 21 figures, published version