alpha plus alpha plus t cluster structures and C-12(0(2)(+))-analog states in B-11

作者:Yamada Taiichi*; Funaki Yasuro
来源:PHYSICAL REVIEW C, 2010, 82(6): 064315.
DOI:10.1103/PhysRevC.82.064315

摘要

The structure of 3/2(-) and 1/2(+) states in B-11 is investigated with an alpha + alpha + t orthogonality condition model (OCM) based on the Gaussian expansion method. Full levels up to the 3/2(3)(-) and 1/2(2)(+) states around the alpha + alpha + t threshold (E-x = 11.1 MeV) are reproduced consistently with the experimental energy levels. It is shown that the 3/2(3)(-) state located around the Li-7 + alpha threshold has an alpha + alpha + t cluster structure, whereas the 3/2(1) and 3/2(2) states have a shell-model-like compact structure. We found that the 3/2(3) state does not possess an alpha-condensate-like nature analogous to the 0(2)(+) state of C-12 (Hoyle state) which has a dilute 3 alpha-condensate structure described by a (0S alpha)(3) configuration with about 70% probability, although the monopole transition strength of the former is as large as that of the latter. We discuss the reasons why the 3/2(3)(-) state does not have the condensate character. On the other hand, the 1/2(1)(+) state just below the 7Li + alpha threshold has a cluster structure that can be interpreted as a parity-doublet partner of the 3/2(3)(-) state. We indicate that the 12.56-MeV state (J(pi) = 1/2(2)(+)) just above the alpha + alpha + t threshold observed in the Li-7(Li-7,B-11*)t reaction, etc., is of the dilute cluster-gas-like configuration and is a strong candidate for the product states of clusters, having a configuration of (0S alpha)(2)(0S(t)) with about 65% probability, from the analyses of the single-cluster motions in B-11. The structure property of the 1/2(+) resonant state is analyzed with the complex scaling method.

  • 出版日期2010-12-27