Decay Pattern of Pygmy States Observed in Neutron-Rich (26)Ne

作者：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

来源：Physical Review Letters, 2008, 101(21): 212503.

DOI：10.1103/PhysRevLett.101.212503

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 (25)Ne+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.

• 出版日期2008-11-21