Isomeric 0- halo-states in 12Be and 11Li

Abstract

We predict the existence of an isomeric 0$^-$-state in $^{12}$Be at an excitation energy of about 2.5 MeV, and a 0$^-$-resonance in $^{11}$Li with both energy and width of about 1 MeV corresponding to two-neutron emission. The structure of these halo-like states are like the 1$^-$-states which means essentially a core surrounded by two neutrons in single-particle $s$ and p-states. The life-time of the $^{12}$Be state is determined by $M1$ or $M2$-emission, $\tau(M1) \approx 10^{-11}$ s or $\tau(M2) \approx 10^{-8}$ s estimated for photon energies of 0.1 MeV and 0.6 MeV, respectively.