The low-lying level structures of $^{ 26}{ \rm Ne}$, $^{ 28}{ \rm Ne}$ and $^{ 30}{ \rm Ne}$ which are related to the breaking of the N=20 shell closure have been studied by the framework of the deformed-basis antisymmetrized molecular dynamics plus generator coordinate method using Gogny D1S force. The properties of the many-particle and many-hole states are discussed as well as that of the ground band. We predict that the negative-parity states in which neutrons are promoted into $pf$-orbit from $sd$ orbit have the small excitation energy in the cases of $^{ 28}{ \rm Ne}$ and $^{ 30}{ \rm Ne}$ which, we regard, is a typical phenomena accompanying the breaking of N=20 shell closure. It is also found that the neutron $4p4h$ structure of $^{ 30}{ \rm Ne}$ appears in low excitation energy which contains $\alpha + ^{ 16}{ \rm O}$ correlations.
Categories: nucl-th