The nuclear shell structure, which originates in the nearly independent motion of nucleons in an average potential, provides an important guide for our understanding of nuclear structure and the ...underlying nuclear forces. Its most remarkable fingerprint is the existence of the so-called magic numbers of protons and neutrons associated with extra stability. Although the introduction of a phenomenological spin-orbit (SO) coupling force in 1949 helped in explaining the magic numbers, its origins are still open questions. Here, we present experimental evidence for the smallest SO-originated magic number (subshell closure) at the proton number six in
C obtained from systematic analysis of point-proton distribution radii, electromagnetic transition rates and atomic masses of light nuclei. Performing ab initio calculations on
C, we show that the observed proton distribution radii and subshell closure can be explained by the state-of-the-art nuclear theory with chiral nucleon-nucleon and three-nucleon forces, which are rooted in the quantum chromodynamics.
The spin-lattice relaxation times
T
1
of an unstable nucleus
19
O (
T
1/2
= 26.9 s,
I
= 5/2) implanted into Y
2
O
3
stabilized ZrO
2
(YSZ), which is a solid oxide fuel cell material, were measured at
...T
= 278 − 333 K by means of the
β
-NMR technique, using a highly spin polarized
19
O beam produced via the heavy ion reaction. The motional correlation times
τ
c
for oxygen motion derived from the
T
1
data are on the same straight line on the Arrhenius plot as those derived from the previous
17
O-NMR data at above the room temperature. This indicates that
19
O ions implanted into YSZ from outside seem to exhibit the same behavior as oxygen ions in the host YSZ material.
We have developed a new and compact β-nuclear magnetic resonance (NMR) system using beta-radioactive nuclei. By using a Halbach array permanent magnet to create a static magnetic field, and a ...scintillating fiber as a detector, we succeeded in significantly reducing the size and weight of the entire system. The performance of the new spectrometer was tested and evaluated by observing an NMR spectrum of
19
O (
T
1/2
= 26.9 s,
I
= 5/2) in TiO
2
.
•We measured the production cross sections for a variety of radioactive isotopes.•They were produced from 124Xe, 48Ca, and 238U beams at 345MeV/nucleon using BigRIPS.•The measured production cross ...sections were compared with the EPAX formulae.•We discovered four new isotopes 85,86Ru and 81,82Mo produced by 124Xe+Be.•103Sb is particle unbound with an upper limit of 49ns for the half-life.
We have measured the production rates and production cross sections for a variety of radioactive isotopes which were produced from 124Xe, 48Ca, and 238U beams at an energy of 345MeV/nucleon using the BigRIPS separator at the RIKEN Nishina Center RI Beam Factory (RIBF). Proton-rich isotopes with atomic numbers Z=40–52 and neutron-rich isotopes with Z=5–16 were produced by projectile fragmentation of the 124Xe and 48Ca beam on Be targets, respectively. Neutron-rich isotopes with Z=20–59 were produced by in-flight fission of the 238U beam, in which both Be and Pb were used as production targets. The measured production rates and production cross sections were compared with those of the LISE++ calculations, and overall fairly good agreement has been obtained. Furthermore, in the measurements with the 124Xe beam, we have discovered four new isotopes on the proton-drip line, 85,86Ru and 81,82Mo, and obtained the clear evidence that 103Sb is particle unbound with an upper limit of 49ns for the half-life. The measurements of projectile-fragment momentum distributions have been also performed with the 124Xe beam, in which the low-momentum tails of the distributions have been measured for the first time at the energy of 345MeV/nucleon.
•Position-sensitive detectors were developed for storage-ring decay spectroscopy.•Fiber scintillation and silicon strip detectors were tested with heavy ion beams.•A new fiber scintillation detector ...showed an excellent position resolution.•Position and energy detection by silicon strip detectors enable full identification.
As next generation spectroscopic tools, heavy-ion cooler storage rings will be a unique application of highly charged RI beam experiments. Decay spectroscopy of highly charged rare isotopes provides us important information relevant to the stellar conditions, such as for the s- and r-process nucleosynthesis. In-ring decay products of highly charged RI will be momentum-analyzed and reach a position-sensitive detector set-up located outside of the storage orbit. To realize such in-ring decay experiments, we have developed and tested two types of high-resolution position-sensitive detectors: silicon strips and scintillating fibers. The beam test experiments resulted in excellent position resolutions for both detectors, which will be available for future storage-ring experiments.
The swelling phenomenon of Si crystal, irradiated by Ar+ and C+ beams, and its morphological change through the thermal annealing process have been studied. The height of swelling structures produced ...by the Ar+ beam is much higher than that produced by the C+ beam at energy 90keV with the fluence up to 8×1016/cm2. The large different in the swelling height was well understood base on the productivity of vacancies evaluated by the SRIM simulation and experiment. Post-implantation samples irradiated with fluence 4×1016/cm2, were annealed at various temperatures in the range of 200–800°C. In the case of Ar+ irradiated samples, the swelling height started to increase at about 600°C. In contrast, in the case of C+ beam irradiated samples, the swelling height started to decrease at about 600°C and almost disappeared at 800°C. The opposite behavior is understood based on the difference in irradiation-induced defect and in rearrangement mechanism in the thermal annealing process.
We have carried out molecular dynamics (MD) simulations of 50
keV accelerated Ar ions, colliding with a Si surface. Using this procedure the amorphous structural region of the Si was found to expand ...with the progression of the interface region, that lie between the amorphous structure and the crystalline structure, as fluence increased in the depth direction. There has been considerable interest in studying the time development of the behavior of sputtered silicon atoms after being subjected to collisions with the Ar ions. Here, by tracking the atoms in the computational domain, clusters formed during sputtering are classified under various kinds. In this process small cluster of atoms e.g., monomer and dimer, and large cluster of atoms in forms of hillocks are formed where the smaller cluster have their energy higher than that of the large cluster.
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