A joint research group of the Institute of Physical and Chemical Research, Tohoku University, Rikkyo University and others has completed a new electron scattering experimental device (new electron microscope) for observing unstable nuclei, and a small amount of xenone (Xe) taken out from an isotope separator. -132 (proton number 54, neutron number 78) We conducted an electron scattering experiment on the nucleus and succeeded in determining the proton distribution.
To see small atoms (1 trillionth of a millimeter in size), a method called "high-energy electron scattering" is used, in which a high-energy electron beam collides with an atomic nucleus and the scattered electrons are investigated.In the past, a thin film of elements was made and irradiated with an electron beam, but the number of atomic nuclei required to be at least 1 to the 10th power.The electron scattering experiment is easy with stable nuclei, but it is completely impossible because it cannot be mass-produced with artificially created unstable nuclei.
Therefore, this time, we are the first in the world to develop a new method called the SCRIT method.It is a method of trapping and concentrating target ions in the path of a thin electron beam, which automatically causes an electron scattering phenomenon.By incorporating this mechanism into an accelerator called an "electron storage ring," electron scattering experiments can be performed with only 1 million target nuclei.
The unstable nuclear electron scattering experimental facility equipped with this SCRIT device was completed at RIKEN Nishina Accelerator Research Center in about 6 years.Using this facility, about 1 million Xe nuclei taken out from the isotope separator ERIS were poured into the SCRIT device, electrons scattered from the nuclei were observed, and the proton distribution of the nuclei was successfully determined from the angular distribution of the scattering. Although Xe is a stable nucleus, since it was tested with exactly the same specifications as the unstable isotope experiment, it will be possible to measure the unstable nuclear proton distribution by starting full-scale unstable nucleation by ERIS.
In the future, the measurement of the proton distribution of unstable nuclei will progress, and it is expected that this facility will become a base for constructing a new nuclear model that comprehensively understands the nuclear structure.
Paper information: [Physical Review Letters] First elastic electron scattering from 132Xe at the SCRIT facility
