Impurity effects of $\Lambda$ particle on the 2$\alpha$ cluster states of $^{9}$Be and $^{10}$Be

Abstract

The low-lying structure of $^{10}_\Lambda$Be and $^{11}_\Lambda$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 $\Lambda$ 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 $\Lambda$ 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.