Borromean structures in medium-heavy nuclei
  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. 
D. Hove, D.V. Fedorov, H.O.U. Fynbo, A.S. Jensen, K. Riisager, N.T.   Zinner, E. Garrido
nucl-th nucl-ex