Cluster states and monopole transitions in ${}^{16}$O

Abstract

Cluster structures and monopole transitions in positive parity states of ${}^{16}$O were investigated based on the generator coordinate method calculation of an extended ${}^{12}$C+$\alpha$ cluster model. The ground and excited states of a ${}^{12}$C cluster are taken into account by using ${}^{12}$C wave functions obtained with the method of antisymmetrized molecular dynamics. The $0_2^{+}$ state of ${}^{16}$O and its rotational members, the $2_1^{+}$ and $4_1^{+}$ states are described well by the cluster states dominated by the ${}^{12}$C($0_1^{+}$)+$\alpha$ structure. Above the ${}^{12}$C($0_2^{+}$)+$\alpha$ threshold energy, we obtained a $0^{+}$ state having the ${}^{12}$C($0_2^{+}$)+$\alpha$ cluster structure, which is considered to be a candidate for the $4\alpha$ cluster gas state. The band structures were discussed based on the calculated $E2$ transition strength. Isoscalar Monopole excitations from the ground state were also discussed.

Comments: 15 pages, 9 figures