Molecular-orbital structure in neutron-rich C isotopes

Abstract

The molecule-like structure of the C isotopes (A=12, 14, 16) is investigated using a microscopic $α+α+α+n+n+\cdot \cdot \cdot$ model. The valence neutrons are classified based on the molecular-orbit (MO) model, and both $π$-orbit 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 3$α$ against the breathing-like break-up. However, $^{14}$C with the $π$-orbit does not show clear energy minimum 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 $^{16}$C with the $(3/2^-_π)^2(1/2^-_σ)^2$ configuration for the four valence neutrons is one of the most promising candidates for such structure.