Negative parity states of ${}^{11}$B and ${}^{11}$C and the similarity with $^{12}C

Abstract

The negative parity states of ${}^{11}$B and ${}^{11}$C were studied based on the calculations of antisymmetrized molecular dynamics(AMD). The calculations well reproduced the experimental strengths of Gamov-Teller(GT), $M1$ and monopole transitions. We, especially, focused on the $3/2_3^{-}$ and $5/2_2^{-}$ states, for which GT transition strengths were recently measured. The weak $M1$ and GT transitions for the $3/2_3^{-}$ in ${}^{11}$B and ${}^{11}$C are described by a well-developed cluster structure of $2\alpha$+$t$ and $2\alpha$+${}^3$He, respectively, while the strong transitions for the $5/2_2^{-}$ is characterized by an intrinsic spin excitation with no cluster structure. It was found that the $3/2_3^{-}$ state is a dilute cluster state, and its features are similar to those of the ${}^{12}$C$(0_2^{+})$ which is considered to be a gas state of three $\alpha$ clusters.

10 pages, 4 figures, submitterd to Physical Review C

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