CLUSTER STRUCTURES IN 3/2- AND 1/2+ STATES OF 11B

Cluster structures of 3/2- and 1/2+ states in 11 B are investigated with a semi-microscopic α + α + t cluster model based on the Gaussian expansion method. The [Formula: see text] state, characterized by the monopole transition strength as large as the Hoyle state ([Formula: see text] at Ex = 7.65 MeV in 12 C ), was found to have a loosely bound α+α+t cluster structure, although its features is not similar to those of the Hoyle state with the dilute 3α-condensate-like character (0Sα)3, in which the α particle is occupied in a single 0S-orbit with about 70% probability. We indicate that the 12.56-MeV state (Jπ = 1/2+) around the α + α +t threshold observed in the 7 Li (7 Li ,11 B *)t reaction etc. is a strong candidate for the Hoyle-analogue state with the main configuration of (0Sα)2(0St) from the analyses of the single-cluster motions in 11 B .

CLUSTER STATES AND ALPHA PARTICLE CONDENSATION IN 13C

The structure of 13 C is studied with the semi-microscopic cluster model, 3α+n orthogonality condition model (OCM). The energy spectra of four 1/2- states and three 1/2+ states up to Ex ~ 13 MeV are successfully reproduced, in particular, three monopole transition strengths are in fair agreement with the observed ones. We discuss the cluster states and alpha particle condensation in the 1/2± states appearing around the 12 C +n, 9 Be +α and 3α+n thresholds.