Effects of $\alpha$-cluster breaking on 3$\alpha$ cluster structures in $^{12}$C

摘要

To clarify the effects of $\alpha$-cluster breaking on 3$\alpha$ clusterstructures in $^{12}$C, we investigate $^{12}$C using a hybrid model thatcombines the Brink-Bloch cluster model with the $p_{3/2}$ subshell closure wavefunction. We have found that $\alpha$-cluster breaking caused by spin-orbitforce significantly changes cluster structures of excited $0^{+}$ statesthrough orthogonality to lower states. Spatially developed cluster componentsof the $0^{+}_{2}$ state are reduced. The $0^{+}_{3}$ state changes from avibration mode in the bending motion of three $\alpha$ clusters to a chain-like3$\alpha$ structure having an open triangle configuration. As a result of thesestructure changes of $0^{+}$ states, the band assignment for the $2^{+}_{2}$state is changed by the $\alpha$-cluster breaking effect. Namely, in modelcalculations without the $\alpha$-cluster breaking effect, the $0^{+}_{2}$state is assigned to be the band-head of the $2^{+}_{2}$ state. However, whenwe incorporate $\alpha$-cluster breaking caused by the spin-orbit force, the$0^{+}_{3}$ state is regarded as the band-head of the $2^{+}_{2}$ state.