Search for low lying dipole strength in the neutron rich nucleus 26Ne Original Research Article

Coulomb excitation of the exotic neutron-rich nucleus 26Ne on a natPb target was measured at 58 A.MeV in order to search for low-lying E1 strength above the neutron emission threshold. Data were also taken on an natAl target to estimate the nuclear contribution. The radioactive beam was produced by fragmentation of a 95 A.MeV 40Ar beam delivered by the RIKEN Research Facility. The set-up included a NaI gamma-ray array, a charged fragment hodoscope and a neutron wall. Using the invariant mass method in the 25Ne+n channel, we observe a sizable amount of E1 strength between 6 and 10 MeV. The reconstructed 26Ne angular distribution confirms its E1 nature. A reduced dipole transition probability of B(E1)=0.49±0.16 e2fm2 is deduced. For the first time, the decay pattern of low-lying strength in a neutron-rich nucleus is obtained. The results are discussed in terms of a pygmy resonance centered around 9 MeV.