Variety of clustering in O 18

We investigate excited states of $^{18}\mathrm{O}$ by using the antisymmetrized molecular dynamics. It is found that five different types of cluster states exist which we call $^{14}\mathrm{C}+\ensuremath{\alpha}$, higher-nodal $^{14}\mathrm{C}+\ensuremath{\alpha}$, two molecular states, and $4\ensuremath{\alpha}$ linear-chain. The calculated $\ensuremath{\alpha}$-decay widths are compared with the observed data. The higher-nodal $^{14}\mathrm{C}+\ensuremath{\alpha}$ cluster states reasonably agree with resonances reported by the recent experiments. We predict that the $\ensuremath{\alpha}$-particle emission is dominant for the $^{14}\mathrm{C}+\ensuremath{\alpha}$ cluster states while the molecular states prefer the $^{6}\mathrm{He}$ emission.