Gibelin J, Beaumel D, Motobayashi T, Blumenfeld Y, Aoi N, Baba H, Elekes Z, Fortier S, Frascaria N, Fukuda N, Gomi T, Ishikawa K, Kondo Y, Kubo T, Lima V, Nakamura T, Saito A, Satou Y, Scarpaci J-A, Takeshita E, Takeuchi S, Teranishi T, Togano Y, Vinodkumar A M, Yanagisawa Y, Yoshida K
Institut de Physique Nucléaire, IN2P3-CNRS, Université Paris Sud, F-91406 Orsay, France.
Phys Rev Lett. 2008 Nov 21;101(21):212503. doi: 10.1103/PhysRevLett.101.212503. Epub 2008 Nov 19.
Coulomb excitation of the exotic neutron-rich nucleus (26)Ne on a (208)Pb target was measured at 58 MeV/u in order to search for low-lying E1 strength above the neutron emission threshold. This radioactive beam experiment was carried out at the RIKEN Accelerator Research Facility. Using the invariant mass method in the 25Ne+n channel, we observe a sizable amount of E1 strength between 6 and 10 MeV excitation energy. By performing a multipole decomposition of the differential cross section, a reduced dipole transition probability of B(E1)=0.49+/-0.16e(2) fm(2) is deduced, corresponding to 4.9+/-1.6% of the Thomas-Reiche-Kuhn sum rule. For the first time, the decay pattern of low-lying strength in a neutron-rich nucleus is measured. The extracted decay pattern is not consistent with several mean-field theory descriptions of the pygmy states.
为了寻找高于中子发射阈值的低激发能E1强度，在理研加速器研究设施中，以58 MeV/u的能量测量了在（208）Pb靶上对富含中子的奇特核（26）Ne的库仑激发。该放射性束流实验得以开展。利用25Ne + n通道中的不变质量法，我们在6至10 MeV激发能之间观测到了可观的E1强度。通过对微分截面进行多极分解，推导出约化偶极跃迁概率B（E1）= 0.49±0.16e（2）fm（2），对应于托马斯 - 赖歇 - 库恩求和规则的4.9±1.6%。首次测量了富含中子核中低激发能强度的衰变模式。提取出的衰变模式与矮态的几种平均场理论描述不一致。
