Pure σ -bond linear chain in C16

A new $\ensuremath{\alpha}$-cluster linear chain is theoretically investigated in $^{16}\mathrm{C}$. By using the antisymmetrized molecular dynamics, we show that a ${(1/{2}_{\ensuremath{\sigma}}^{\ensuremath{-}})}^{2}{(1/{2}_{\ensuremath{\sigma}}^{+})}^{2}$ linear-chain configuration exists with extreme deformation. It is compared with a 27.2 MeV state observed by a recent cluster-decay experiment $^{2}\mathrm{H}(^{16}\mathrm{C},^{4}\mathrm{He}+^{12}\mathrm{Be}$ or $^{6}\mathrm{He}+^{10}\mathrm{Be})^{2}\mathrm{H}$. We show that a decay pattern of this new linear-chain configuration---it dominantly decays into the $^{6}\mathrm{He}+^{10}\mathrm{Be}({0}_{2}^{+})$ channel---is in good agreement with the observed data.