No abstract

No abstract

In a recent breakup-reaction experiment using a Be12 beam at 29  MeV/nucleon, the 0+ band head of the expected He4+He8 molecular rotation was clearly identified at about 10.3 MeV, from which a large monopole matrix element of 7.0±1.0  fm2 and a large cluster-decay width were determined for the first time. These findings support the picture of strong clustering in Be12, which has been a subject of intense investigations over the past decade. The results were obtained thanks to a specially arranged detection system around zero degrees, which is essential in determining the newly emphasized monopole strengths to signal the cluster formation in a nucleus.

After magnetic separation, identification through time of flight and 5E x E measurements has allowed the observation of the new nuclei, 29F, 35'36Mg, 3s'39A1, 4~ 43,44p, 45'46'47S, 46'4v'4s'49C1, 49'5~ from the interaction of a 4SCa beam of 55 MeV/u with tantalum targets.

A new 11 Be(d, p) 12 Be transfer reaction experiment was carried out in inverse kinematics at 26.9A MeV, with special efforts devoted to the determination of the deuteron target thickness and of the required optical potentials from the present elastic scattering data. In addition a direct measurement of the cross section for the 0 + 2 state was realized by applying an isomer-tagging technique. The s-wave spectroscopic factors of 0.20 +0.03 −0.04 and 0.41 +0.11 −0.11 were extracted for the 0 + 1 and 0 + 2 states, respectively, in 12 Be. Using the ratio of these spectroscopic factors, together with the previously reported results for the p-wave components, the single-particle component intensities in the bound 0 + states of 12 Be were deduced, allowing a direct comparison with the theoretical predictions. It is evidenced that the ground-state configuration of 12 Be is dominated by the d-wave intruder, exhibiting a dramatic evolution of the intruding mechanism from 11 Be to 12 Be, with a persistence of the N = 8 magic number broken.