Indication of dilute $2\alpha+t$ cluster structure in $^{11}$B
T. Kawabata, H. Akimune, H. Fujita, Y. Fujita, M. Fujiwara, K. Hara, K. Hatanaka, Motoharu Itoh, Yoshiko Kanada-En’yo, S. Kishi, Kotaro Nakanishi, H. Sakaguchi, Y. Shimbara, A. Tamii, S. Terashima, Makoto Uchida, T. Wakasa, Y. Yasuda, Hidetomo P. Yoshida, M. Yosoi · arXiv (Cornell University) · 2005
The cluster structures of the excited states in $^{11}$B are studied by analyzing the isoscalar monopole and quadrupole strengths in the $^{11}$B($d$,$d'$) reaction at $E_d=200$ MeV. The excitation strengths are compared with the theoretical predictions by the shell-model and antisymmetrized molecular-dynamics (AMD) calculations. It is found that the large monopole strength for the $3/2^-_3$ state at $E_x=8.56$ MeV is well described by the AMD wave function with a dilute $2\\alpha+t$ cluster structure. The $5/2^-_2$ state at $E_x=8.92$ MeV is suggested to have a mixing structure both with the cluster and shell-model wave functions.