Gamma-ray spectroscopy on neutron-rich nuclei via RI beam fragmentation method

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The research results obtained in this research project are summarized in the following two points.1.Development of RI beams and discovery of new neutron-rich isotopes.To apply the RI beam fragmentation method for heavier neutron rich nudei with N=28, we developed RI beams by using an intense 48Ca beams, which is appropriate for efficient productions of the nuclei. According to a new acceleration scheme realized at RIKEN, the beam intensity was increased by about two orders of magnitudes. To use the intense beam, we searched for new neutron-rich isotopes. As a result, we found for the first time ^<84>Ne, ^<87>Na and ^<48>Si. In addition, we found that ^<88>Ne, ^<86>Na and ^<89>Mg are particle-unbound nuclei. The fact of the particle stability for ^<48>Si suggests a possible magicity-loss in the Z〜14 and N〜28 region. All of the findings were shown in a Journal paper as well as in a press conference.2.Development of new techniques for measuring mean-lives of excited statesTo overcome disadvantages in the RI beam fragmentation method, we developed two new methods to measure mean-lives of excited states, Doppler Shift Attenuation Method (DSAM) and the Recoil Shadow Method CRSM). These two methods were applied for two light nuclei, ^<12>Be and ^<16>C. We found that the mean-life of the first excited state of 180 is surprisingly long. This new challenging are being supported by the Grant-in-Aid for Scientific Research (A)(2) 16204017.