2α+t cluster structure in 11B

Abstract The cluster structures of the excited states in 11 B are studied by analyzing the isoscalar monopole and quadrupole strengths in the B 11 ( d , d ′ ) reaction at E d = 200 MeV . The excitation strengths are compared with the predictions by the shell-model and antisymmetrized molecular-dynamics (AMD) calculations. The large monopole strength for the 3 / 2 3 − state at E x = 8.56 MeV is well described by the AMD calculation and is suggested to be an evidence for a well developed 2 α + t cluster structure.