Resonance structure of 9Be and 10Be in a microscopic cluster model

Structure of the excited states in Be-9 and Be-10 have been theoretically explored by means of the alpha+alpha+n and alpha+alpha+n+n microscopic cluster models, respectively. Resonance excited states in Be-9 and Be-10 are localized by solving the two-body scattering problems of [Be-8+n]circle plus[He-5+alpha] and [Be-9+n]circle plus[He-6+alpha], respectively. Our models have reproduced satisfactorily the experimental low-energy spectrum in Be-9 and given various resonance excited states in Be-10. Our model shows that the two and three competing configurations are quite essential in order to reproduce the anomalous 1/2(+) state in Be-9 and the second 0(+) state in Be-10, respectively. One of these configurations has a strong Be-8 core distortion that is induced by the valence neutron and is known to be responsible for lowering the s(1/2) orbit in these states. Another configuration produces a spatially extended neutron distribution outside the Be-8 core like the neutron halo.