A variety of clustering in ${}^{18}$O

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