Cluster structure in light neutron-rich nuclei

Abstract

Recently, discussions of the well-developed cluster structure are extended to the neutron-rich C isotopes, and the role of valence neutrons which stabilize the linear-chain structure has been pointed out. Here, we perform a microscopic calculation for the Be isotopes and the C isotopes and study these well-developed molecular-like states. The appearance of prolonged structure with the α-α core in 10Be [1] and 12Be [2] is shown to be successfully described by the α + α + n + n + ··· model, where the orbits for the valence neutrons are classified based on the molecular-orbit (MO) model. The molecule-like structure of the C isotopes has been also investigated using a microscopic α + α + α + n + n + ··· model [3], where both norbit and σ-orbit are introduced around three α-clusters. The valence neutrons which occupy the π-orbit increase the binding energy and stabilize the linear-chain of 3α against the breathing-like break-up. However, 14C with the π-orbit does not show clear minimal energy against the bending-like path. The combination of the valence neutrons in the π- and the σ-orbit is promising to stabilize the linear-chain state against the breathing- and bending-modes, and it is found that the excited states of 16C is one of the most promising candidates for such structure.