National Superconducting
Cyclotron Laboratory

Kei Minamisono
Kei Minamisono
Research Senior Physicist and Adj. Professor of Physics
Experimental Nuclear Physics
PhD, Physics, Osaka University, 1999
Joined NSCL in October 2004
Phone (517) 908-7145
Fax (517) 353-5967
Office 1047
minamiso at nscl.msu.edu

Kei Minamisono

One of my current research interests is to determine fundamental properties of very rare isotopes. Particularly I am interested in the size and shape of a nucleus, which tells us how nucleons distribute inside a nucleus. Experimental determination of size of nucleus is essential to gain critical insights into the driving force of the structural change toward the limit of nucleus.

Here is one example: the radii of very light mass, proton-rich calcium isotopes, which is shown in the figure. Experimental charge radii show a very intricate pattern as more neutrons are added. The 48Ca nucleus, for example has almost the same radius as 40Ca with eight more neutrons are added! Nuclear scientists consider the chain of Ca radii as a “text book” example of how the nuclear structure effect emerges in the radii, and is challenging nuclear theories. For such system, we determined radii of proton-rich Ca isotopes. They turned out to be very compact and surprisingly small compared with the previous theory, adding a new puzzle. An improved theory had to be developed, correctly taking into account the weak binding of protons, that is the coupling with the proton continuum. The improved theory now successfully explains the general trend of radii from proton-rich 36Ca to neutron-rich 52Ca isotopes.

We perform experiments at the BEam COoling and LAser spectroscopy (BECOLA) facility at NSCL. We illuminate laser light on an atom and measure fluorescence from the perturbed atom due to the interplay between the orbital electron and nucleus. The fluorescence contains information about the size of a nucleus. Technical development is another essential aspect of our group to efficiently determine a radius. Therefore developments of laser techniques and production of stable-isotope beams are critical.
Students in my group will have an opportunity to gain hands-on experience in running laser spectroscopy experiments for radius measurements. It includes, for example operation of the laser system, ion beam production from an offline ion source and ion-beam transport, the DAQ system and analysis/interpretation of obtained data.

Ca isotopes

Charge radii of calcium isotopes are shown. Experimental charge radii show a very intricate pattern as more neutrons are added (the 48Ca nucleus, for example has almost the same radius as 40Ca with eight more neutrons are added!). The chain of Ca radii has been considered as a "text book" example of how the nuclear structure effect emerges in the radii, and challenging nuclear theories. For such system, we determined radii of proton-rich Ca isotopes (solid red circles). They turned out to be very compact and surprisingly small compared with the previous theory. An improved theory, correctly taking into account the weak binding of protons, that is the coupling with the proton continuum, successfully explains not only the proton-rich but also the neutron rich Ca isotopes.  

Selected Publications

Ground-state electromagnetic moments of 37Ca, A. Klose et al., Phys. Rev. C 99, 061301(R) (2019).

Proton superfluidity and charge radii in proton-rich calcium isotopes, A. J. Miller et al., Nature Physics 15, 432 (2019).

First determination of ground state electromagnetic moments of 53Fe, A. J. Miller et al., Phys. Rev. C 96, 054314 (2017).

Charge radii of neutron deficient 52,53Feproduced by projectile fragmentation, K. Minamisono et al., Phys. Rev. Lett. 117, 252501 (2016).

Charge radii of neutron-deficient 36K and 37K, D.M. Rossi et al., Phys. Rev. C 92, 014305 (2015).