Triaxial deformation in 10Be

Abstract

The triaxial deformation in ${}^{10}$Be is investigated using a microscopic $\alpha +\alpha +n+n$ model. The states of two valence neutrons are classified based on the molecular-orbit (MO) model, and the $\pi$-orbit is introduced about the axis connecting the two $\alpha$-clusters for the description of the rotational bands. There appear two rotational bands comprised mainly of $K^{\pi }=0^{+}$ and $K^{\pi }=2^{+}$, respectively, at low excitation energy, where the two valence neutrons occupy $K^{\pi }=3/2^{-}$ or $K^{\pi }=1/2^{-}$ orbits. The triaxiality and the $K$-mixing are discussed in connection to the molecular structure, particularly, to the spin-orbit splitting. The extent of the triaxial deformation is evaluated in terms of the electro-magnetic transition matrix elements (Davydov-Filippov model, Q-invariant model), and density distribution in the intrinsic frame. The obtained values turned out to be $\gamma =15^o\sim 20^o$.

Comments: 15 pages, latex, 3 figures