Breaking of N=8 magicity in 13Be

The structure of ¹³Be was investigated with antisymmetrized molecular dynamics. The variation after spin and parity projections was performed. An unnatural parity 1/2^- state was suggested to be lower than the 5/2⁺ state indicating that vanishing of the N=8 magic number occurs in ¹³Be. A low-lying 3/2⁺ state with a 2ℏω configuration was also suggested. Developed cluster structures were found in the intruder states. The lowering mechanism of the intruder states was discussed in terms of molecular orbitals around a 2α core.