Three-center cluster states in ¹¹C and ¹¹B

Structures of excited states in ¹¹C and ¹¹B were studied based on variational calculations after spin-parity projection in a framework of antisymmetrized molecular dynamics (AMD). The calculations systematically reproduce experimental data of the transition strengths such as Gamov-Teller(GT) and M1 transitions. A well-developed cluster structure of 2α+³He(t) was found in the state of ¹¹C(¹¹B). We assigned this state to the observed state at 8 MeV. The calculations reproduce the small which has been measured in the recent experiments. It was found that the state has a dilute cluster state, and its features are similar to those of the which is considered to be a gas state of three α clusters.