Coexistence of α+α+n+n and α+t+t cluster structures in 10Be

The coexistence of the α+α+n+n and α+t+t cluster structures in the excited states of 10Be has been discussed. In the previous analysis, all the low-lying states of 10Be were found to be well described by the motion of the two valence neutrons around two α clusters. However, the α+t+t cluster structure was found to coexist with the α+α+n+n structure around Ex=15 MeV, close to the corresponding threshold. We have introduced a microscopic model to solve the coupling effect between these two configurations. The K=0 and K=1 states are generated from the α+t+t configurations due to the spin coupling of two triton clusters. The present case of 10Be is one of the few examples in which completely different configurations of triton-type (α+t+t three-center) and α-type (α+α+n+n two-center) clusters coexist in a single nucleus in the same energy region