Hironori Iwasaki

Professor, Department of Physics & Astronomy
Location: 1012 Cyclotron Bldg
Profile photo of  Hironori Iwasaki
Photo of: Hironori Iwasaki


My research has focused on spectroscopy of exotic nuclei far from stability. Unstable nuclei with very unusual proton-to-neutron ratios, called "exotic nuclei", often show surprising phenomena, presenting important challenges for our understanding of atomic nuclei. The goal of present-day nuclear physics is to establish the unified understanding of nuclear structure for stable and exotic nuclei, by exploring the isospin degree-of-freedom of the shell structure and collective properties of nuclei. The physics outputs thus serve as vigorous tests for modern nuclear theories, as well as provide answers to questions concerning the nature of neutron stars and the origin of the elements in the Universe. Nuclear structure information can also be used to make tests of fundamental symmetries that describe the weak and strong forces in nature.

At NSCL, my group performs in-beam gamma and particle spectroscopy with rare isotope beams, with an emphasis on lifetime measurements for nuclear levels. Lifetimes for bound levels are closely related to transition probabilities between the relevant states, which provide sensitive probes for anomaly in structure of exotic nuclei, for example, shape coexistence, changes of magic numbers, and proton-neutron decoupling phenomena, and so on. For unbound levels, lifetimes can be associated with the energy uncertainties to be measured as the resonance widths, which play important roles in the stability of extreme quantum systems as well as in nuclear reaction rates of astrophysical interest.

Challenges in experimental studies for level lifetime measurements are to develop methodology and detection system, which are suitable for the use with rare isotope beams. Typical level lifetimes range from 1 nanosecond (10-9 s) to 1 femtosecond (10-15 s) for bound levels, and for resonances, lifetimes can be even 1 zeptosecond (10-21 s).

# Education:
* 2001: Ph.D., University of Tokyo


  • PHY 492: Intro to Nuclear Physics
  • PHY 802: Survey of Nuclear Physics

Selected Publications

  • Breakdown of the Z=8 Shell Closure in Unbound 12O and its Mirror Symmetry, D.Suzuki, H.Iwasaki et al., Phys.Rev.Lett. 103, 152503 (2009)
  • Lifetime measurements of first excited states in 16C, 18C, H.J.Ong et al., Phys.Rev. C 78, 014308 (2008)
  • Low-Lying Neutron Intruder State in 13B and the Fading of the N = 8 Shell Closure, H.Iwasaki et al., Phys.Rev.Lett. 102, 202502 (2009)
  • Low-lying proton intruder state in 13B, S.Ota et al., Phys.Lett. B 666, 311 (2008)
  • Persistence of the N=50 shell closure in the neutron-rich isotope 80Ge, H.Iwasaki et al., Phys.Rev. C 78, 021304(R) (2008)