Publisher：Interactions  

We are developing a laser spectroscopic method to study the nuclear structure of radioactive isotopes utilizing superfluid helium (He II) as an efficient stopper for highly energetic ion beams and as an in-situ laser spectroscopic environment. Recently, we conducted an ion stopping experiment for the 84Rb37+ beams with the energy of approximately 350 A MeV at QST-HIMAC with a cryostat system used for 66 A MeV at RIKEN-RIPS experiment (Appl. Phys. Express 12, 016502 (2019)). The radioactive 84Rb ions were produced via a projectile fragmentation reaction using accelerated 84Kr36+ beams and a 12-mm thick Be target. As a first step, we measured the stopping range distribution of the injected ion beams in liquid N2 to estimate the stopping range distribution in He II and the spot size of the injected ion beams using a plastic scintillator. Then, a laser-induced fluorescence (LIF) detection experiment was performed using He II. We successfully observed the LIF from 84Rb atoms. We estimated the longitudinal range straggling of 84Rb ions in superfluid helium from the obtained results. The details of experiment at QST-HIMAC and results are given in this report.

DOI： 10.1007/s10751-024-01889-y

Scopus

Publisher：Physical Review C  

Atomic masses of the neutron-rich isotopes Ga83,84, Ge82-86, As82-89, Se82,84-91, Br85,86,89-92, Kr89,91,92, and Rb91 have been measured with high precision and accuracy using the multi-reflection time-of-flight mass spectrograph at the RIBF facility. The masses of As88,89 were measured for the first time and the mass uncertainties of Ge86 and Se90,91 were significantly reduced from several hundred keV to below the 10 keV scale. Investigation of shell evolution and potential subshell closures are proceeded by analysis of two-neutron separation energy systematics. As a result of the precise mass measurements, no prominent change on the slope of the two-neutron separation energy beyond N=56 is observed in Se isotopes, indicating the subshell closure effect at N=56 of Se does not exist. Also, various leading mass models are compared with the measurements. The impact of the more precisely known data on r-process nucleosynthesis calculations is investigated in light of these new mass measurements, showing a remarkable reduction of reaction-rate uncertainties.

DOI： 10.1103/PhysRevC.109.035804

Web of Science

Scopus

Language：English   Publisher：Scientific Reports  

To detect and track structural changes in atomic nuclei, the systematic study of nuclear levels with firm spin-parity assignments is important. While linear polarization measurements have been applied to determine the electromagnetic character of gamma-ray transitions, the applicable range is strongly limited due to the low efficiency of the detection system. The multi-layer Cadmium-Telluride (CdTe) Compton camera can be a state-of-the-art gamma-ray polarimeter for nuclear spectroscopy with the high position sensitivity and the detection efficiency. We demonstrated the capability to operate this detector as a reliable gamma-ray polarimeter by using polarized 847-keV gamma rays produced by the 56Fe(p,p′γ) reaction. By combining the experimental data and simulated calculations, the modulation curve for the gamma ray was successfully obtained. A remarkably high polarization sensitivity was achieved, compatible with a reasonable detection efficiency. Based on the obtained results, a possible future gamma-ray polarimetery is discussed.

DOI： 10.1038/s41598-024-52692-2

Web of Science

Scopus

PubMed

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevC.108.054312

Publisher：Physical Review C  

The ground-state magnetic dipole moment of the neutron-rich O21 isotope has been measured via β-ray-detected nuclear magnetic resonance (β-NMR) spectroscopy by using a spin-polarized secondary beam of O21 produced from the Ne22 primary beam. From the present measurement, the g factor |gexp(Og.s.21)|=0.6036(14) has been determined. Based on the comparison of this value with Schmidt values, we unambiguously confirm the νd5/2 configuration with spin and parity assignments Iπ=5/2+ for the O21 ground state, suggested by previously reported studies. Consequently, the magnetic moment has been determined as μexp(Og.s.21)=(-)1.5090(35)μN. The obtained experimental magnetic moment is in good agreement with the predictions of the shell-model calculations using the USD, YSOX, and SDPF-M interactions as well as random phase approximation (RPA) calculations. This observation indicates that the O21 nucleus in its ground state does not manifest any anomalous structure and is not influenced by the proximity of the drip line.

DOI： 10.1103/PhysRevC.107.024306

Web of Science

Scopus

Event date： 2023.5

Language：English   Presentation type：Oral presentation (general)  

Country：Germany  

Event date： 2023.11 - 2023.12

Language：English   Presentation type：Oral presentation (general)  

Country：United States  

Event date： 2023.11

Language：English   Presentation type：Oral presentation (invited, special)  

Venue： The Nara Kasugano International Forum IRAKA   Country：Japan  

Event date： 2022.9

Language：English   Presentation type：Oral presentation (general)  

Country：South Africa  

Publisher：Interactions  

The original version of this article unfortunately contained mistakes. The corrections are given in the following list: (1) The author name ‘A. Gladkov’ was incorrectly written as ‘A. Gradkov’. (2) The ‘Availability of data and materials’ statement was incorrectly given as ‘No datasets were generated or analysed during the current study’ but should have been ‘The data that support the findings of this study are available from the corresponding author upon reasonable request’. The original article has been corrected.

DOI： 10.1007/s10751-024-01894-1

Scopus