Kenji Katori

Experiment on the Synthesis of Element 113 in the Reaction 209Bi(70Zn,n)278113

The convincing candidate event of the isotope of the 113th element, 278 113, and its daughter nuclei, 274 111 and 270 Mt, were observed, for the first time, in the 209 Bi + 70 Zn reaction at a beam energy of 349.0 MeV with a total dose of 1.7 ×10 19 . Alpha decay energies and decay times of the candidates, 278 113, 274 111, and 270 Mt, were (11.68 ±0.04 MeV, 0.344 ms), (11.15 ±0.07 MeV, 9.26 ms), and (10.03 ±0.07 MeV, 7.16 ms), respectively. The production cross section of the isotope was deduced to be 55 +150 -45 fb (10 -39 cm 2 ).

New Result in the Production and Decay of an Isotope, 278113, of the 113th Element

An isotope of the 113th element, i.e., 278 113, was produced in a nuclear reaction with a 70 Zn beam on a 209 Bi target. We observed six consecutive α-decays following the implantation of a heavy particle in nearly the same position in the semiconductor detector under an extremely low background condition. The fifth and sixth decays are fully consistent with the sequential decays of 262 Db and 258 Lr in both decay energies and decay times. This indicates that the present decay chain consisted of 278 113, 274 Rg ( Z =111), 270 Mt ( Z =109), 266 Bh ( Z =107), 262 Db ( Z =105), and 258 Lr ( Z =103) with firm connections. This result, together with previously reported results from 2004 and 2007, conclusively leads to the unambiguous production and identification of the isotope 278 113 of the 113th element.

Study of halo structure of 16C from reaction cross section measurement

Abstract The reaction cross sections for 12,16 C have been measured at the energy of 83 A MeV by a new experimental method. The larger enhancement of the 16 C reaction cross section at the low energy has been used to study the density distribution ofxa0 16 C. The finite-range Glauber-model calculations for different density distributions have been compared with the experimental data. The analysis suggests that 16 C mainly has a 14 C(core) + 2n structure and shows a strong contribution of (2s1/2)2 for valence neutrons. A large extension of the neutron density distribution to a distance far from the center of the nucleus suggests the formation of neutron halo in the 16 C nucleus.

Anisotropy of conversion electrons from vibrational levels and rotational levels excited by (p, 2n) reactions

Abstract The vibrational levels and the rotational levels in medium and heavy nuclei were excited by (p, 2n) reactions with 14.3 MeV protons. The anisotropy of the conversion electrons from the excited states was observed by means of a double focussing beta-ray spectrometer. The observed anisotropy showed systematic features, depending on the spins of the target, the excited levels associated with the transition and the multipolarity. The analysis of the anisotropy was made in terms of the statistical continuum theory. The systematical trend of the observed anisotropy was reproduced by the calculations. The angular distribution of the gamma rays from such nuclear reactions was found to be very useful for the study of the properties of the residual excited state and the transition.

Energy-level structure of O19, O18 and O17 investigated by (d, p) reactions with 15 MeV deuterons

Abstract The reactions O18(d, p)O19, O17(d, p)O17 were studied with 14.95 MeV deuterons and a broad range magnetic spectrograph. Absolute cross sections were measured. Angular distributions were analysed with the Butler-Born theory to determine reduced widths. In O18(d, p)O19 reactions, energies (MeV), ln and Jπ of O19 levels obtained are as follows: 0, 2, 5 2 + ; 0.096, (2), 3 2 + ; 1.468, 0, 1 2 + ; (2.612); 3.171, 1; 3.942; 4.111, (1); 5.153; 5.447, 2, 3 2 + ; (5.708); 6.282, 3, 7 2 − ; (6.480); (6.560); (6.899); 6.997; (7.117); 7.248. Assignments in parenthesis are not definitely established. From O17(d, p)O18 reactions, 4.440, 1, (3)−; 5.092; (5.375); 5.492; 6.200 are obtained. In O16(d, p)O17 reactions, intense transitions with ln = 2 to the ground 1 d 5 2 and 5.083 MeV 1 d 3 2 states and with ln = 0 to 0.871 MeV 2s state are observed, giving 1d and 2s single-particle reduced widths. A strong ln = 3 transition proceeded to 5.697 MeV ( Jπ = 7 2 − ) level, while the transition intensity for the lower 7 2 − (3.846 MeV) level was 0.18 times as weak. In O18(d, p)O19 reactions, the single-particle character of four strongly excited levels of O19 and their correspondence to those of O17 are discussed. An estimate is made of the configuration admixtures in the O18 ground state taking into account O18(d, t)O17 reaction data. The presence of 24±6% (1 f 7 2 2 ) 0 component (in intensity) is concluded. The experimentally determined admixtures are compared with shell-model calculations. The measured spectroscopic factors for the transitions to the three lowest levels of O19 can be interpreted with available shell-model wave functions of these states and of the O18 ground state.

Conversion Electrons from (p, 2n) and (α, 3n) Reactions on Vibrational Nuclei

The structure of excited states in neutron deficient nuclei was investigated by observing conversion electrons from the ( p , 2 n ) and (α, 3 n ) reactions on vibrational nuclei. Momentum spectra of the conversion electrons were measured by means of a sector-type beta-ray spectrometer. Intensity ratios of the conversion electrons were analyzed in terms of the statistical model. The systematic trend of levels in the neutron deficient Te isotopes is discussed. The existence of a new deformed region is suggested between the neutron numbers N =50 and N =82.

The Spin-Spin Interaction of 0.92 MeV Polarized Neutrons with Polarized 165Ho Nuclei

In order to obtain a direct measure of the strength and form of the nuclear spin-spin interaction, the transmission of 0.92 MeV polarized neutrons by polarized 165 Ho was measured. The total cross section and relative scattering angular distribution of 0.92 MeV unpolarized neutrons through unpolarized 165 Ho nuclei were also measured in order to make a parameter search of the optical potential. The experimental results are analyzed with Davies and Satchlers DWBA formalism. The results show that the effective spin-spin interaction between a free neutron and a 165 Ho nucleus, is an attraction type and its strength has the order of one MeV, and the present experimental result together with other data obtained at ORNL and Stanford, can be fitted by the DWBA approach in either case of a volume and surface type of the form factor. For the further determination of the strength and the form of the spin-spin interaction, more precise similar experiments are needed for various different neutron energies.

Experiment on Elastic Scattering of Protons by O18

The differential cross section for the elastic scattering of protons by O 18 has been measured for proton energies from 600 to 1450 keV at center-of-mass angles of 140.8° and 90.0°. Targets consisted of thin LiOH films on thin gold foils and BeO films on thick beryllium foils. The technique for the preparation of these thin O 18 targets is described. Protons scattered elastically from O 18 were selected by a 90°-magnetic spectrometer. Resonances were observed at 633, ∼680, ∼850, 987, 1169, 1239 and 1403 keV in proton energies, indicating the excitation of seven levels of the compound nucleus, F 19 . The resonance near 850 keV showed a marked anomaly with large width, and the resonance near 680 keV was a weakly excited one with large width. Other resonances had weakly excited anomalies with small widths.

NEUTRON DEPOLARIZATION IN ELASTIC SCATTERING.

The depolarization parameter D (θ) in elastic scattering of 1.36 MeV neutrons was measured at θ 2 =30°, 38°, 80°, 120° and 150° for 27 Al, 59 Co, 63,65 Cu, 209 Bi and Ni nuclei. The departure of D (θ) from unity for Al, Co, Cu and Bi was observed particularly at backward angles, but not observed for Ni. This fact shows that the spin flip of incident neutrons takes place along the normal to the scattering plane in the elastic scattering process for non-zero spin targets. These results are discussed in the light of different nuclear reaction mechanisms.

ELASTIC AND INELASTIC SCATTERING OF PROTONS ON

Excitation functions for elastic scattering of protons on Ne 22 were studied at θ c.m. =56.9°, 92.6°, 125.7°, 140.8° and 151.3° in the energy range E p =0.94–4.2 MeV. The excitation function for protons inelastically scattered to the first excited state of Ne 22 was measured at θ lab. =139.1° above E p =2.1 MeV and the γ rays following them were observed below E p =2.1 MeV. A total of 75 resonances was observed corresponding to Na 23 levels between 9.7 MeV and 12.8 MeV. Several pronounced resonances are analysed using the single level approximation of the dispersion formula, and level parameters are assigned. The T =3/2 isobaric analogue states in Na 23 and Ne 23 are discussed.