An exclusive measurement has been made of the Coulomb dissociation of the two-neutron halo nucleus 11Li at 70 MeV/nucleon at RIKEN. Strong low-energy (soft) E1 excitation is observed, peaked at about Ex = 0.6 MeV with B(E1) = 1.42(18) e2fm2 for Erel < or = 3 MeV, which was largely missed in previous measurements. This excitation represents the strongest E1 transition ever observed at such low excitation energies. The spectrum is reproduced well by a three-body model with a strong two-neutron correlation, which is further supported by the E1 non-energy-weighted cluster sum rule.

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The BigRIPS in-flight separator, which became operational in March 2007 at the RI Beam Factory (RIBF) at RIKEN Nishina Center, has been used to produce a variety of rare-isotope (RI) beams by using in-flight fission as well as projectile fragmentation. Its major features are large ion-optical acceptances and two-stage structure. Excellent performance in particle identification is also an important feature. Efficient RI-beam production based on the in-flight scheme has been made possible by these features of the BigRIPS separator, allowing us to greatly expand the accessible region of exotic nuclei. An RI-beam delivery line following the BigRIPS separator is designed to work as a forward spectrometer, called ZeroDegree. As a major experimental device at RIBF, the ZeroDegree spectrometer has been used for a variety of reaction studies with RI beams. In this paper, we present an overview of the BigRIPS separator and the ZeroDegree spectrometer, emphasizing the capability and potential of the new-generation RI beam facility, RIBF.

A candidate resonant tetraneutron state is found in the missing-mass spectrum obtained in the double-charge-exchange reaction ^{4}He(^{8}He,^{8}Be) at 186  MeV/u. The energy of the state is 0.83±0.65(stat)±1.25(syst)  MeV above the threshold of four-neutron decay with a significance level of 4.9σ. Utilizing the large positive Q value of the (^{8}He,^{8}Be) reaction, an almost recoilless condition of the four-neutron system was achieved so as to obtain a weakly interacting four-neutron system efficiently.