Radioactive Isotope Physics Laboratory

This laboratory explores exotic nuclear structures and dynamics in unstable nuclei that have never been investigated before, such as those with largely imbalanced proton and neutron numbers. Our aim is to develop new experimental techniques utilizing fast RI beams to discover new phenomena and properties in unstable nuclei. Another important subject is the equation-of-state of asymmetric nuclear matter, and its association with the origin of elements and with neutron stars. For instance, we are making attempts to the better understand underlyning mechanism for exotic stability-enhancements of very neutron-rich fluorine isotopes, the large deformation of the nucleus 34Mg with N=22 in spite of its vicinity to the N=20 magic neutron number and anomalous collectivity in 16C. We are further extending these studies to medium- and heavy-mass regions by developing facilities, detectors and unique methods at RIBF, thereby leading on the challenging task to find new exotic phenomena. We also perform numerical simulations of nucleosynthesis under the environment of core-collapse supernovae, and moreover quest for footprints of supernovae and solar activities in the past, embedded in Antarctic ice core, in collaboration with Cosmic radiation laboratory and National Institute of Polar Research.

Research Subjects

• Study of structure and dynamics of unstable nuclei through development of new methods utilizing fast RI beamsI beams
• Stability of exotic nuclei and exploration into limit of nuclear existence
• Research on equation-of-state in asymmetric nuclear matter via heavy-ion induced reaction
• Promotion of nuclear astrophysics in an interdisciplinary organization

Publications

1. Nishimura S., Li Z, Watanabe H., Yoshinaga K, et al.:
   "Beta-Decay Half-Lives of Very Neutron-Rich Kr to Tc Isotopes on the Boundary of the r-Process Path: An Indication of Fast r-Matter Flow"
   Phys. Rev. Lett. 106, 052502 (2011)
2. Doornenbal P, Scheit H, Aoi N, Takeuchi S, et al.:
   "Spectroscopy of Ne-32 and the "Island of Inversion""
   Phys. Rev. Lett. 103, 152503 (2009)
3. Suzuki D., Iwasaki H., Otsu H., et al.:
   "Breakdown of the Z=8 Shell Closure in Unbound O-12 and its Mirror Symmetry"
   Phys. Rev. Lett. 103, 152503 (2009)
4. Suzuki D., Iwasaki H., Ong HJ., Imai N., Sakurai H., Nakao T., Aoi N., Baba H., et al.:
   "Lifetime measurements of excited states in C-17:Possible interplay between collectivity and halo effects"
   Physics Letters B 666, 222-227 (2008)
5. Ong, H. J., Imai, N., Suzuki D., Iwasaki H., Sakurai H., Onishi T.K., Suzuki M.K., Ota S., Takeuchi S., Nakao T., et al.:
   "Lifetime measurements of first excited states in C-16, C-18"
   Physical Review C 78, 014308 (2008)
6. Madokoro, H., Shimizu, T., and Motizuki, Y.:
   "Importance of prolate neutrino radiation in core-collapse supernovae: the reason for the prolate geometry of SN1987A?"
   Pub. Astron. Soc. Japan, 56, 663-669 (2004)
7. T.K. Onishi, A. Gelberg, H. Sakurai et al.:
   "Gamow-Teller decay of the T=1 nucleus 46Cr"
   Phys. Rev. C 72, 024308 (2005)
8. Notani, M., Sakurai, H., Aoi, N., Yanagisawa, Y., Saito, A., Imai, N., Gomi, T., Miura, M., Michimasa, S., Iwasaki, H., Fukuda, N., Ishihara, M., Kubo, T., Kubono, S., Kumagai, H., Lukyanov, S.M., Motobayashi, T., Onishi, T.K., Penionzhkevich, Yu.E., Shim.:
   "New neutron-rich isotopes, 34Ne, 37Na and 43Si, produced by fragmentation of a 64A MeV 48Ca beam"
   Physics Letters B 542, 49-54 (2002).
9. Yoneda, K., Sakurai, H., Gomi, T., Motobayashi, T., Aoi, N., Fukuda, N., Futakami, U., Gacsi, Z., Higurashi, Y., Imai, N., Iwasa, N., Iwasaki, H., Kubo, T., Kunibu, M., Kurokawa, M., Liu, Z., Minemura, T., Saito, A., Serata, M., Shimoura, S., Takeuchi, S.:
   "Deformation of 34Mg studied via in-beam -ray spectroscopy using RI beam fragmentation"
   Physics Letters B 499, 233-237 (2001).
10. Sakurai, H., Lukyanov, S.M., Notani, M., Aoi, N., Beaumel, D., Fukuda, N., Hirai, M., Ideguchi, E., Imai, N., Ishihara, M., Iwasaki, H., Kubo, T., Kusaka, K., Kumagai, H., Nakamura, T., Ogawa, H., Penionzhkevich, Yu.E., Teranishi, T., Watanabe, Y.X., Yone.:
    "Evidence for particle stability of 31F and particle instability of 25N and 28O"
    Physics Letters B 448, 180-184 (1999).