Structure studies of 13 Be from the 12 Be β’(π,π) reaction in inverse kinematics on a solid deuteron target
The low-lying structure of 13 Be has remained an enigma for decades. Despite numerous experimental and theoretical studies, large inconsistencies remain. Being both unbound and one neutron away from 14 Be, the heaviest bound beryllium nucleus, 13 Be is difficult to study through simple reactions with weak radioactive-ion beams or more complex reactions with stable-ion beams. Here, we present the results of a study using the 12 Be (π,π)β’ 13 Be reaction in inverse kinematics using a 9.5 MeV per nucleon 12 Be beam from the ISAC-II facility. The solid deuteron target of IRIS was used to achieve an increased areal thickness compared to conventional deuterated polyethylene targets. The π-value spectrum below β4.4 MeV was analyzed using a Bayesian method with geant4 simulations. A three-point angular distribution with the same π-value gate was fit with a mixture of π - and π-wave, π - and π-wave, or pure π-wave transfer. The π-value spectrum was also compared with geant simulations obtained using the energies and widths of states reported in four previous works. As a result, it was found that our results are incompatible with works that revealed a wide 5/2 + resonance but shows better agreement with ones that reported a narrower width.