A. Kusoglu, D.L. Balabanski, R.Z. Hu, S. Q. Fan, F.R. Xu, P. Constantin, P.-A. Soderstrom, M. Cuciuc, S. Aogaki, R.S. Ban, R. Borcea, A. Coman, R. Corbu, C. Costache, A. Covali, I. Dinescu, N.M. Florea, V. Iancu, A. Ionescu, N.M. Marginean, C. Mihai, R.E. Mihai, C.V. Nedelcu, T. Petruse, H. Pai, A. Pappalardo, O.A. Sirbu, C.O. Sotty, L. Stan, A.N. State, D.A. Testov, T. Tozar, A. Turturica, G. Turturica, S. Ujeniuc, C.A. Ur, V. Vasilca, F. Zhu [ https://link.aps.org/doi/10.1103/PhysRevLett.133.072502 ]
Scientists from the Gamma Driven Experiments Department (GDED) group have started experimental campaigns in 2022 using a hybrid array of large-volume ELI-NP LaBr3:Ce and CeBr3 and ROSPHERE HPGe detectors placed in BGO anti-Compton shields creating a unique worldwide experimental setup, which provides unprecedented γ-ray efficiency for high-energy γ-rays at IFIN 9 MV Tandem.
Within the first experimental campaign, excited states in 10B were populated with the 10B(p, p'γ)10B reaction at 8.5 MeV, and their γ decay was investigated via the method of coincidence γ-ray spectroscopy.
The state-of-art spectrometer allowed the observation of weak γ-ray transitions, such as the M3 transition between the Jπ, T = 01+, 1 isobaric analog state (IAS) and the Jπ, T = 31+
0 ground state which competes with an M1 transition to the first excited Jπ, T = 11+, 0 state and the E2 transition between the Jπ, T = 21+, 0 state and the IAS, i.e., performing measurements of branching ratios at the level of 10-5.
For the first time in 10B, the competing M1 and isospin-forbidden M3 transitions from the decay of the IAS have been observed in an γ spectroscopy experiment. As a result, clustering effects in both the 31+, 0 gs, and the 01+, 1 IAS are suggested to enhance the M3 transition.
Ab initio no-core shell model calculations were performed by Ronghze Hu and Siqin Fan under the supervision of Prof. Furong Xu from Peking University by using the newest version of the local position-space chiral N3LO nucleon-nucleon interaction. The earlier versions of the N3LO NN force without the inclusion of the 3N force cannot reproduce the correct 31+, 0 ground state and the correct order of the levels in 10B. As a result of this Letter, the calculations reproduce correctly the ordering of the bound states in 10B, and they are in reasonable agreement with the experimentally observed branching ratios and reduced transition probabilities.
As a follow-up, an invitation came from the Science Bulletin in the News & Views section to present findings and discuss the highlights of the research in the light nuclei in Ref. (A. Kusoglu, Science Bulletin (2024) in print).
https://doi.org/10.1016/j.scib.2024.08.040
Fig.1 - Experimental bound excited states of 10B compared with the NCSM calculation with the newest version of the local position-space chiral N^3LO NN force
Fig.2 - The γ-ray spectrum observed in coincidence with the 414 keV γ-ray transition of 10B. The 10B γ rays are labeled with their energies. The peaks marked with the triangles indicate contamination.
