The low-lying structures of ${}_{\mathrm{\Lambda }}{}^{10}\mathrm{Be}$ and ${}_{\mathrm{\Lambda }}{}^{11}\mathrm{Be}$ are investigated within the framework of the antisymmetrized molecular dynamics. We focus on the modifications of the excitation spectra and dynamical changes of the $2\alpha$ cluster structure caused by a $\mathrm{\Lambda }$ particle as an impurity in these hypernuclei. It is found that the excitation energies of well-pronounced cluster states are largely shifted up by the addition of a $\mathrm{\Lambda }$ particle. Furthermore, we also find that the $2\alpha$ cluster structure is significantly changed in the excited states, whereas it is almost unchanged in the ground states.

• Received 23 June 2015

DOI:https://doi.org/10.1103/PhysRevC.92.044326