Cluster structures in 11B

Structures of excited states in B-11 are investigated with a method of beta-gamma constraint antisymmetrized molecular dynamics in combination with the generator coordinate method. Various excited states with developed cluster core structures are suggested in positive- and negative-parity states. For negative-parity states, we suggest a band with a 2 alpha + t cluster structure. This band starts from the 3/2(3)(-) state and can correspond to the experimental band observed recently. In positive-parity states, two alpha core cluster structures with surrounding nucleons are found. A K-pi = 1/2(+) band is suggested to be constructed from a remarkably developed cluster structure with a large prolate deformation. We discuss features of the cluster structure in association with molecular orbital structures of Be-10.