Monopole transitions to cluster states in $^{10}$Be and $^9$Li

Abstract

Isoscalar monopole transitions from the ground states to cluster states in $\Be$ and $\Li$ are investigated with $\He+\alpha$ and $\He+t$ cluster models, respectively. In $\Be$, significant monopole strengths to $\He+\alpha$ cluster resonances of $\Be(0^+_{3,4})$ above the $\alpha$-decay threshold are obtained, whereas those to $\He+t$ cluster resonances in $^9$Li are not enhanced because of the large fragmentation of the strengths in the corresponding energy region. The monopole transition to $\Be(0^+_2)$ having the molecular orbital structure is relatively weak compared with those to $\He+\alpha$ cluster resonances. Monopole strength distributions do not directly correspond to distributions of $\He(0^+)+\alpha$ and $\He(0+)+t$ components but they reflect component of the deformed $\He$ cluster with a specific orientation, which is originally embedded in the ground state.