First excited 1/2(+) state in B-9

Abstract

Evidence has been found for a broad unbound state near 1 MeV excitation in 9B that is a candidate for the long-disputed 12 mirror of the unbound 1.68 MeV state in 9Be. Reactions of 6Li 6Li were studied with a 60 MeV beam incident on a 240 μg/cm2 6LiF target. The breakup fragments from the decay of the reaction products were detected in five Si-Si-CsI telescope detectors and the breakup particles were reconstructed using the technique of resonant particle spectroscopy. It is shown that contrary to a previous study, the 12 is not populated in the reaction 6Li(6Li,t)9B, but that it is populated via the 6Li(6Li,d)10B reaction. The sequential decays of 10B populated the channels 6Li(g.s.)+α, 6Li(2.186 MeV)+α, 8Be+d, and pnαα, with the latter including (9B+n or 9Be+p) decay from 10B. Decays through 9B are identified and show the presence of the 12 state as a broad asymmetric peak around 0.8-1.0MeV with Γ 1.5 MeV. © 2012 American Physical Society.

Document Downloads