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.

No abstract

No abstract

No abstract

No abstract

An inelastic excitation experiment was performed with a 12 Be beam at 29 MeV/u on a carbon target. New resonances close to the respective cluster separation thresholds were observed in 12 Be for the 4 He + 8 He and 6 He + 6 He decay channels, confirming the previously proposed molecular rotational bands. Using the model-independent angular correlation analysis, a 0 + spin parity is assigned to the remarkably large peak at 10.3 MeV in the 4 He + 8 He channel. A distorted wave Born approximation (DWBA) calculation was compared to the experimental differential cross section of this state, resulting in a largely enhanced monopole transition matrix element of 7.0 ± 1.0 fm 2 , in good agreement with the generalized two-center cluster model (GTCM) prediction assuming a preformed α-4n-α configuration. Together with the previously reported large cluster spectroscopic factor, the strong clustering in 12 Be is well demonstrated. The detection focused on the most forward angles, by using a zero-deg telescope, is essential in the present measurement.