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Structure of the mirror nuclei $^9$Be and $^9$B in a microscopic cluster model

K. Arai·Y. Ogawa·Y. Suzuki·K. Varga
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Abstract

The structure of the mirror nuclei $^9$Be and $^9$B is studied in a microscopic $α+ α+ n$ and $α+ α+ p$ three-cluster model using a fully antisymmetrized 9-nucleon wave function. The two-nucleon interaction includes central and spin-orbit components and the Coulomb potential. The ground state of $^9$Be is obtained accurately with the stochastic variational method, while several particle-unbound states of both $^9$Be and $^9$B are investigated with the complex scaling method.The calculation for $^9$Be supports the recent identification for the existence of two broad states around 6.5 MeV, and predicts the $\frac{3}{2}^{-}_2$ and $\frac{5}{2}^{-}_2$ states at about 4.5 MeV and 8 MeV, respectively. The similarity of the calculated spectra of $^9$Be and $^9$B enables one to identify unknown spins and parities of the $^9$B states. Available data on electromagnetic moments and elastic electron scatterings are reproduced very well. The enhancement of the $E$1 transition of the first excited state in $^9$Be is well accounted for. The calculated density of $^9$Be is found to reproduce the reaction cross section on a Carbon target. The analysis of the beta decay of $^9$Li to $^9$Be clearly shows that the wave function of $^9$Be must contain a small component that cannot be described by the simple $α+ α+ n$ model. This small component can be well accounted for by extending a configuration space to include the distortion of the $α$-particle to $t+p$ and $h+n$ partitions.

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K. Arai, Y. Ogawa, Y. Suzuki, K. Varga. 1996-04-09. Structure of the mirror nuclei $^9$Be and $^9$B in a microscopic cluster model. https://doi.org/10.1103/physrevc.54.132

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