Structure of the mirror nucleiBe9andB

Abstract

The structure of the mirror nuclei 9 Be and 9 B is studied in a microscopic ␣ϩ␣ϩn and ␣ϩ␣ϩp threecluster model using a fully antisymmetrized nine-nucleon wave function. The two-nucleon interaction includes central and spin-orbit components together with 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 3/2 2 Ϫ and 5/2 2 Ϫ states at about 4.5 MeV and 8MeV, 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 E1 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 ␣ϩ␣ϩn model. This small component can be well accounted for by extending a configuration space to include the distortion of the ␣ particle to tϩ p and hϩn partitions. ͓S0556-2813͑96͒02607-6͔

6He-triton cluster states in9Li

“…In preceding works [3][4][5][6][7][8][9][10]18], the K π = 0 + 2 band of 10 Be is considered to be a molecular orbital state having two valence neutrons in the molecular σ orbital around the 2α cluster core. In the case that α-α distance is moderate, the configuration (a) in Fig.…”

“…Many of low-lying states of Be isotopes are understood in a molecular orbital picture where a Be nucleus is considered to consist of 2 α's and valence neutron(s) in molecular orbitals around the 2α core [1][2][3][4][5][6][7][8][9][10][11][12][13]. In highly excited states near the He+He threshold energy of 10 Be and 12 Be, well-developed cluster states have been suggested experimentally and theoretically [7,[12][13][14][15][16][17][18][19][20].…”

Formation and decay of resonance states in Be9 and B9 nuclei: Microscopic three-cluster model investigations

“…In addition, we search for the Hoyle-analog states in 9 Be and 9 B. There are many attempts to study the resonance structure of 9 Be and 9 B within various methods and models [5][6][7][8][9][10][11][12][13]. Those investigations have been dominantly performed within the cluster model and different variants of the resonating group method.…”

α- 5 He decaying states and the ground-state rotational band of 9 Be

“…From the spectra it was not possible to conclude, whether the broad peak centered between 6 and 7 MeV is due to two levels at these excitations as claimed in [6,7] or to a single broad state [8]. It may be added that three different theoretical calculations [10,17,18] predict the 7 2 − and 9 2 + states at these energies to be very close to each other (∆E ≤ 400 keV).…”

“…In the most recent one [10] the widths were also calculated and the − state (2.9 and 1.2 MeV). However, the same theories also predict several other states of 9 Be but their existence has not been confirmed experimentally.…”