4$\alpha$ linear-chain state produced by ${}^9$Be+${}^9$Be collision

Extreme nuclear deformations provide great insight into the geometric formation of quantum many-body systems. In this work, the $4\alpha +2n$ linear chain is assessed in ${}^{18}$O. We predict excitation energies, moment-of-inertia, $\alpha$-, and ${}^9$Be-decay widths by using the antisymmetrized molecular dynamics. We show that the $K^{\pi }=3^{-}$ linear-chain states may be verified by the head-on ${}^9\mathrm{B}\mathrm{e}+{}^9\mathrm{B}\mathrm{e}$ collision experiments.