Molecular-orbital structure in neutron-rich C isotopes

The moleculelike structure of the C isotopes (A = 12, 14, 16) is investigated using a microscopic alpha + alpha + alpha + n + n + ... model. The valence neutrons are classified based on the molecular-orbit model, and both pi orbit and sigma orbit are introduced around three alpha clusters. The valence neutrons which occupy the pi orbit increase the binding energy and stabilize the linear chain of 3 alpha against the breathinglike breakup. However, C-14 With the pi orbit does not show a clear energy minimum against the bendinglike path. The combination of the valence neutrons in the pi and sigma orbits is promising to stabilize the linear-chain state against the breathing and bending modes, and it is found that the excited states of C-16 with the (3/2(pi)(-))(2)(1/2(sigma)(-))(2) configuration for the four valence neutrons is one of the most promising candidates for such a structure.