DOI： 10.7566/JPSJ.87.014202

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The isospin characters of low-energy dipole excitations in neutron-rich unstable nucleus O-20 were investigated, for the first time in unstable nuclei. Two spectra obtained from a dominant isovector probe (O-20 + Au) and a dominant isoscalar probe (O-20 + alpha) were compared and analyzed by the distorted-wave Born approximation to extract independently the isovector and isoscalar dipole strengths. Two known 1(-) states with large isovector dipole strengths at energies of 5.36(5) MeV (1(1)(-)) and 6.84(7) MeV (1(2)(-)) were also excited by the isoscalar probe. These two states were found to have different isoscalar dipole strengths, 2.70(32)%(1(1)(-)) and 0.67(12)%(1(2)(-)), respectively, in exhaustion of the isoscalar dipole-energy-weighted sum rule. The difference in isoscalar strength indicated that they have different underlying structures. (C) 2017 The Author(s). Published by Elsevier B.V.

DOI： 10.1016/j.physletb.2017.03.017

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© 2016 American Physical Society. The proton-proton momentum correlation functions [Cpp(q)] for the kinematically complete decay channels Al23→p+p+Na21 and Mg22→p+p+Ne20 have been measured at the RIKEN RI Beam Factory. From the very different correlation strength of Cpp(q) for Al23 and Mg22, the source size and emission time information were extracted from the Cpp(q) data by assuming a Gaussian source profile in the correlation function calculation code (crab). The results indicated that the mechanism of two-proton emission from Al23 was mainly sequential emission, while that of Mg22 was mainly three-body simultaneous emission. By combining our earlier results of the two-proton relative momentum and the opening angle, it is pointed out that the mechanism of two-proton emission could be distinguished clearly.

DOI： 10.1103/PhysRevC.94.044621

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Language：English   Publisher：AMER PHYSICAL SOC  

DOI： 10.1103/PhysRevC.93.049904

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

The low-lying level structures of nuclei in the vicinity of Ni-78 were investigated using in-beam gamma-ray spectroscopy to clarify the nature of the nuclear magic numbers Z = 28 and N = 50 in systems close to the neutron drip line. Nucleon knockout reactions were employed to populate excited states in Zn-80 and Zn-82. A candidate for the 4(1)(+) level in Zn-80 was identified at 1979(30) keV, and the lifetime of this state was estimated to be 136(-67)(+92) ps from a line-shape analysis. Moreover, the energy of the 2(1)(+) state in Zn-82 is reported to lie at 621(11) keV. The large drop in the 2(1)(+) energy at Zn-82 indicates the presence of a significant peak in the E(2(1)(+)) systematics at N = 50. Furthermore, the E(4(1)(+))/E(2(1)(+)) and B(E2; 4(1)(+) -> 2(1)(+))/B(E2; 2(1)(+) -> 0(g.s.)(+)) ratios in Zn-80 were deduced to be 1.32(3) and 1.12(-60)(+80), respectively. These results imply that Zn-80 can be described in terms of two-proton configurations with a 78Ni core and are consistent with a robust N = 50 magic number along the Zn isotopic chain. These observations, therefore, indicate a persistent N = 50 shell closure in nuclei far from the line of beta stability, which in turn suggests a doubly magic structure for Ni-78.

DOI： 10.1103/PhysRevC.93.024320

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/jpsgaiyo.71.1.0_331

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

In proton therapy, positron emitter nuclei are generated via the target nuclear fragmentation reactions between irradiated proton and nuclei constituting a human body. The proton-irradiated volume can be con-firmed with measurement of annihilation γ-rays from the generated positron emitter nuclei. To achieve the high accuracy of proton therapy, in vivo dosimetry,i.e., evaluation of the irradiated dose during the treat-ment is important. To convert the measured activity distribution to irradiated dose, cross-sectionaldata for positron emitter production is necessary, which is currently insufficient in the treatment area. The purpose of this study is to collect cross-sectionaldata of 12C(p, pn)11Cand 12C(p, p2n)10Creactions between the incident proton and carbon nuclei, which are important target nuclear fragmentation reactions, to estimate the range and exposure dose distribution in the patient’s body. Using planar-type PET capable of measuring annihilation γ-rays at high positional resolution and thick polyethylene target, we measured cross-sectionaldata in continuous wide energy range. The cross section of 12C(p, pn)11Cis in good agreement with exist-ing experimental data. The cross section of 12C(p, p2n)10Cis reported for the first data in the low-energyrange of 67.6–10.5MeV near the Bragg peakof proton beam.

DOI： 10.1016/j.nuclphysa.2015.11.0070375-9474

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© 2015 The Authors. Two-proton relative momentum (qpp) and opening angle (θpp) distributions from the three-body decay of two excited proton-rich nuclei, namely Al23→p+p+Na21 and Mg22→p+p+Ne20, have been measured with the projectile fragment separator (RIPS) at the RIKEN RI Beam Factory. An evident peak at qpp20MeV/cas well as a peak in θpparound 30° are seen in the two-proton break-up channel from a highly-excited22Mg. In contrast, such peaks are absent for the23Al case. It is concluded that the two-proton emission mechanism of excited22Mg is quite different from the23Al case, with the former having a favorable diproton emission component at a highly excited state and the latter dominated by the sequential decay process.

DOI： 10.1016/j.physletb.2015.02.066

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/jpsgaiyo.70.2.0_213

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Publishing type：Research paper (international conference proceedings)  

Excited states in the nuclei 38,40,42 Si have been studied using in-beam Γ-ray spectroscopy following multi-nucleon removal reactions to investigate the systematics of excitation energies along the Z=14 isotopic chain. The most probable candidates for the transition from the yrast 4 + state were tentatively assigned among several γ lines newly observed in the present study. The energy ratios between the 21+ and 41+ states were obtained to be 2.09(5), 2.56(5) and 2.93(5) for 38,40,42Si, respectively, indicating a rapid development of deformation in Si isotopes from N=24 to, at least, N=28. © Owned by the authors, published by EDP Sciences, 2014.

DOI： 10.1051/epjconf/20146602070

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：E D P SCIENCES  

Excited states in the nuclei Si-38,Si-40,Si-42 have been studied using in-beam gamma-ray spectroscopy following multi-nucleon removal reactions to investigate the systematics of excitation energies along the Z = 14 isotopic chain. The most probable candidates for the transition from the yrast 4(+) state were tentatively assigned among several gamma lines newly observed in the present study. The energy ratios between the 2(1)(+) and 4(1)(+) states were obtained to be 2.09(5), 2.56(5) and 2.93(5) for Si-38,Si-40,Si-42, respectively, indicating a rapid development of deformation in Si isotopes from N = 24 to, at least, N = 28.

DOI： 10.1051/epjconf/20146602070

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

The applicability of Coulomb dissociation reactions to determine the cross section for the inverse neutron capture reaction was explored using the reaction Li-8(gamma,n)Li-7. A 69.5 MeV/nucleon Li-8 beam was incident on a Pb target, and the outgoing neutron and Li-7 nucleus were measured in coincidence. The deduced (n,gamma) excitation function is consistent with data for the direct capture reaction Li-7(n,gamma) Li-8 and with low-energy effective field theory calculations.

DOI： 10.1103/PhysRevC.88.065808

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

The structure of the neutron-rich nucleus Ti-58 was investigated via proton inelastic scattering in inverse kinematics at a mean energy of 42.0 MeV/nucleon. By measuring the deexcitation gamma rays, three transitions with the energies of 1046(11) keV, 1376(18) keV, and 1835(27) keV were identified. The angle-integrated cross section for the 1046-keV excitation, which corresponds to the decay from the first 2(+) state, was determined to be 13(7) mb. The deformation length delta(p,p') was extracted from the cross section to be 0.83(-0.30)(+0.22) fm. The energy of the first 2(+) state and the delta(p,p') value are comparable to the ones of Ti-56, which indicates that the collectivity of the Ti isotopes does not increase significantly with neutron number until N = 36. This fact indicates that Ti-58 is outside of the region of the deformation known in the neutron-rich nuclei around N = 40.

DOI： 10.1103/PhysRevC.88.024326

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

A search for isomeric gamma decays among fission fragments from 345 MeV/nucleon U-238 has been performed at the RIKEN Nishina Center RI Beam Factory. Fission fragments were selected and identified using the superconducting in-flight separator BigRIPS and were implanted in an aluminum stopper. Delayed gamma rays were detected using three clover-type high-purity germanium detectors located at the focal plane within a time window of 20 mu s following the implantation. We identified a total of 54 microsecond isomers with half-lives of similar to 0.1-10 mu s, including the discovery of 18 new isomers in very neutron-rich nuclei: Ti-59(m), As-90(m), Se-92(m), Se-93(m), Br-94(m), Br-95(m), Br-96(m), Rb-97(m), Nb-108(m), Mo-109(m), Ru-117(m), Ru-119(m), Rh-120(m), Rh-122(m), Pd-121(m), Pd-124(m), Ag-124(m), and Ag-126(m), and obtained a wealth of spectroscopic information such as half-lives, gamma-ray energies, gamma-ray relative intensities, and gamma gamma coincidences over a wide range of neutron-rich exotic nuclei. Proposed level schemes are presented for Ti-59(m), Ga-82(m), Br-92(m), Br-94(m), Br-95(m), Rb-97(m), Rb-98(m), Nb-108(m), Zr-108(m), Mo-109(m), Ru-117(m), Ru-119(m), Rh-120(m), Rh-122(m), Pd-121(m), Ag-124(m), and Ag-125(m), based on the obtained spectroscopic information and the systematics in neighboring nuclei. The nature of the nuclear isomerism is discussed in relation to the evolution of nuclear structure.

DOI： 10.1103/PhysRevC.86.054319

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

The reduced transition probability B(E2; 0(gs)(+) -> 2(1)(+)) for S-28 was obtained experimentally using Coulomb excitation at 53 MeV/nucleon. The resultant B(E2) value 181(31) e(2)fm(4) is smaller than the expectation based on empirical B(E2) systematics. The double ratio vertical bar M-n/M-p vertical bar/(N/Z) of the 0(gs)(+) -> 2(1)(+) transition in S-28 was determined to be 1.9(2) by evaluating the M-n value from the known B(E2) value of the mirror nucleus Mg-28, showing the hindrance of proton collectivity relative to that of neutrons. These results indicate the emergence of the magic number Z = 16 in the vertical bar T-z vertical bar = 2 nucleus S-28.

DOI： 10.1103/PhysRevLett.108.222501

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DOI： 10.1063/1.4764205

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

The stellar reaction Si-26(p,gamma) P-27 was studied in the Coulomb dissociation of P-27. Two known resonance levels in P-27 were excited and a candidate for the third excited state was found in the Si-26 p relative energy spectrum. The E2 resonance strengths omega gamma were obtained to be (6.5 +/- 1.3) x 10(-11), (6.0 +/- 1.1) x 10(-10), and (1.10 +/- 0.27) x 10(-10) MeV. The total (E2 + M1)omega gamma value for the first excited state was evaluated to be 1.9(-1.1)(+1.9) x 10(-9) MeV with the help of the shell model. The error was estimated from the deviation of theoretical predictions with the same shell model from experimental strengths obtained in the present study for P-27 and earlier ones for the mirror nucleus Mg-27. The astrophysical reaction rate for the Si-26(p,gamma) P-27 reaction was also calculated and compared with previous estimations.

DOI： 10.1103/PhysRevC.84.035808

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCIENCE PRESS  

Two-proton relative momentum distributions from the break-up channels Al-23 -> p+p+Na-21 and Mg-22 -> p+p+Ne-20 at an energy of 60-70 A MeV have been measured together with two-proton opening angles at the projectile fragment separator beamline (RIPS) in the RIKEN Ring Cyclotron Facility. The results demonstrate the existence of diproton emission component from single-step He-2 for highly excited Al-23 and Mg-22.

DOI： 10.1007/s11433-011-4452-4

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IOP PUBLISHING LTD  

Coulomb dissociation of the proton-rich nucleus Cl-31 was studied experimentally using a Cl-31 beam at 58 MeV/nucleon with a lead target. The relative energy spectrum of S-30+p system was obtained from the measured momentum vectors of the reaction products detected in coincidence by the invariant mass method. The first excited state in Cl-31 was observed which is relevant to the resonant capture in the stellar S-30(p, gamma)Cl-31 reaction. Discussion for another observed state is also given.

DOI： 10.1088/1742-6596/312/4/042025

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC JAPAN  

A search for new isotopes using in-flight fission of a 345 MeV/nucleon U-238 beam has been carried out at the RI Beam Factory at the RIKEN Nishina Center. Fission fragments were analyzed and identified by using the superconducting in-flight separator BigRIPS. We observed 45 new neutron-rich isotopes: Mn-71, Fe-73,Fe-74, Co-76, Ni-79, Cu-81,Cu-82, Zn-84,Zn-85, Ga-87, Ge-90, Se-95, Br-98, Kr-101, Rb-103, Sr-106,Sr-107, Y-108,Y-109, Zr-111,Zr-112, Nb-114,Nb-115, Mo-115,Mo-116,Mo-117, Tc-119,Tc-120, (121,122,123),Ru-124, Rh-123,Rh-124,Rh-125,Rh-126, Pd-127,Pd-128, Cd-133, Sn-138, Sb-140, Te-143, I-145, Xe-148, and Ba-152.

DOI： 10.1143/JPSJ.79.073201

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Publishing type：Research paper (international conference proceedings)  

The Coulomb dissociation of the proton-rich nucleus 31Cl was studied experimentally using a 31Cl beam at 58 MeV/nucleon with a lead target. The relative energy spectrum between 30S ions and protons was obtained from the measured momentum vectors of the reaction products detected in coincidence by the invariant mass method. The first excited state in 31Cl was observed which is relevant to the resonant capture in the stellar 30S(p, γ)31Cl reaction. Discussion for another observed state is also given. © Copyright owned by the author(s).

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DOI： 10.1142/S0217732310000496

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DOI： 10.1063/1.3442626

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DOI： 10.1142/S0218301310015400

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DOI： 10.1142/S0218301310016259

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

Proton inelastic scattering on the neutron-rich nucleus Mg-32 has been studied at 46.5 MeV/nucleon in inverse kinematics. Populated states were identified by measuring de-excitation gamma rays, in which five new states were found by gamma-gamma coincidence analyses. By analyzing the angular differential cross sections via coupled-channel calculations, their spins and parities were constrained and the amplitudes for each transition were extracted. The spin and parity of the 2321-keV state was assigned as 4(1)(+). The ratio between the energies of the 2(1)(+) and 4(1)(+) states indicates that Mg-32 is a transitional nucleus rather than an axially deformed rigid rotor. The collectivities in the nucleus Mg-32 with N=20 are discussed based on the results obtained in the present experiment.

DOI： 10.1103/PhysRevC.79.054319

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

The structure of neutron-rich isotopes Cr-60 and Cr-62 was studied via proton inelastic scattering in inverse kinematics. The deformation lengths (delta) for Cr-60 and Cr-62 were extracted as 1.12(16) and 1.36 (14) fm, respectively, providing evidence for enhanced collectivity in these nuclei. An excited state at 1180(10) keV in Cr-62 was identified for the first time. We adopted 4(+) as its spin and parity, leading to the rapid increase of the E-x(4(+))/E-x(2(+)) ratio, which indicates the development of large deformation in Cr-62 near N = 40. Importance of the admixture of the gd-shell component above N = 40 is also discussed by comparing with a modern shell model calculation.

DOI： 10.1103/PhysRevLett.102.012502

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

Coulomb excitation of the proton-rich nucleus Mg-20 was studied using a radioactive Mg-20 beam at 58A MeV impinging on a lead target. The reduced transition probability B(E2; 0(g.s.)(+) -> 2(1)(+)) was extracted to be 177(32) e(2) fm(4), which agrees with the theoretical predictions by a cluster model assuming O-16 + 2p + 2p structure, a mean-field approach based on the angular momentum projected generator coordinate method, and the USD shell model. The ratio of the neutron-to-proton multipole matrix elements M-n/M-P in the mirror nucleus O-20 was deduced to be 2.51(25) with the M-n value evaluated from the measured B(E2) value for Mg-20 with the help of isospin symmetry. The results confirm the large M-n/M-p value previously reported in O-20, leading to the dominant role of the four valence nucleons in the 2(1)(+) excitation and persistence of the O-16 core in O-20 and Mg-20.

DOI： 10.1103/PhysRevC.78.024306

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC JAPAN  

A search for new isotopes using in-flight fission of a 345 MeV/nucleon U-238 beam has been carried Out in the commissioning experiment of the next-generation in-flight radioactive isotope beam separator BigRIPS at the RI Beam Factory at the RIKEN Nishina Center. Two neutron-rich palladium isotopes Pd-125 and Pd-126 were observed for the first time, which demonstrates the great potential of the RIKEN RI beam Factory.

DOI： 10.1143/JPSJ.77.083201

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

DOI： 10.1103/PhysRevC.78.029902

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.63.1.1.0_68_1

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DOI： 10.1016/j.nuclphysa.2008.02.280

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Other Link： http://orcid.org/0000-0002-7291-7809

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Isoscalar monopole and dipole responses in unstable nucleus O-14 have been studied for a wide excitation energy range by inelastic a scattering at 60 A MeV in inverse kinematics. In order to deduce isoscalar compressional strengths, the multipole decomposition analysis was carried out and the DWBA calculation for isoscalar excitation was studied. Result from the multipole decomposition analysis, isoscalar monopole and dipole strengths were identified corresponding to 63 +/- 12% and 109 +/- 15% of energy-weighted sum rule in E = 4.6-25.0 MeV, respectively, for the measured decay channels of O-14* -> N-13 + p, C-12 + p + p, C-12(1)* + p + p, C-10 + alpha, and C-10(1)* + alpha.

DOI： 10.1016/j.nuclphysa.2007.01.081

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DOI： 10.1063/1.2713519

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Nuclear Society  

Secondary neutron-production cross sections have been measured from interactions of 230 MeV/nucleon He, 400 MeV/nucleon N, 400 MeV/nucleon Kr, 400 MeV/nucleon Xe, 500 MeV/nucleon Fe, and 600 MeV/nucleon Ne interacting in a variety of elemental and composite targets. We report the double-differential production cross sections, angular distributions, energy spectra, and total cross sections from all systems. Neutron energies were measured using the time-of-flight technique and were measured at laboratory angles between 5 and 80 deg. The spectra exhibit behavior previously reported in other heavy-ion-induced neutron-production experiments, namely, a peak at forward angles near the energy corresponding to the beam velocity, with the remaining spectra generated by preequilibrium and equilibrium processes. The double-differential spectra are fitted with a moving-source parameterization. Observations on the dependence of the total cross sections on target and projectile mass are discussed.

DOI： 10.13182/NSE07-A2719

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

For the first time to our knowledge the target screening effect on the pre-emission of halo neutrons from Li-11 has been quantitatively analyzed. Our work has been performed in the 7.5-15 MeV neutron energy range. In this range the target nuclei are likely to behave as opaque, and therefore the sharp-cutoff calculations are most appropriate for the target screening determination. It has been observed that the zeta probability used in the sharp-cutoff calculations is an observable of the experiment, because it can be directly obtained from measured quantities, which are the number of single detected neutrons and the number of detected neutron pairs. The value of zeta(exp) obtained this way in the case of a Si target appears to be close to the zeta value calculated for the Li-11 halo radius R-H=4.8 fm, independently determined in another experiment [Phys. Lett. B287, 307 (1992)]. This property also allows investigation of Borromean halo nuclei such as He-6, Be-14, and B-17, for which R-H was not yet measured. The calculated value within the present approach of the two-neutron pre-emission yield appears to be 3.5 times larger in the case of C-12 than in the case of a Si target.

DOI： 10.1103/PhysRevC.73.057601

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

The Coulomb dissociation of (27)P was studied experimentally using (27)P beams at 57 MeV/nucleon with a lead target. The E2 gamma decay width of the first excited state in (27)P was determined to be (2.8 +/- 0.5) x 10(-5) eV. The total (M1 + E2) gamma decay width of the state, which is of astrophysical interest, is estimated by combining the experimental result and a shell model calculation. The reaction rate of (26)Si(p, gamma)(27)P is deduced from the estimated total gamma decay width. The astrophysical implication derived from estimated gamma decay width is discussed.

DOI： 10.1140/epja/i2006-08-036-3

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

In this paper we present first results from a (8)Li electromagnetic neutron-breakup experiment. Specific reactions studied were Pb((8)Li,(7)Li+n)Pb and C((8)Li,(7)Li+n)C at 41 MeV/nucleon beam energy. This is an effort to compare the results of a Coulomb dissociation experiment with the well determined (n, gamma) reaction cross sections at astrophysical energies. The angular dependence of the cross section above 7 degree, which is the grazing angle of (8)Li-Pb system, is similar in shape for lead and carbon and approximately proportional to A(2/3) in magnitude indicating that the nuclear dissociation is the main component in this region. At very forward angles the angular distributions differ significantly and the electromagnetic dissociation dominates for the lead, although the nuclear contribution is not negligible.

DOI： 10.1140/epja/i2006-08-033-6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

Secondary neutron-production cross sections have been measured from interactions of 290 MeV/nucleon C and 600 MeV/nucleon Ne in a target composed of simulated Martian regolith and polyethylene, and from 400 MeV/nucleon Ne interactions in wall material from the International Space Station. The data were measured between 5 degrees and 80 degrees in the laboratory. We report the double-differential cross sections, angular distributions, and total neutron-production cross sections from all three systems. The spectra from all three systems exhibit behavior previously reported in other heavy-ion neutron-production experiments, namely, a peak at forward angles near the energy corresponding to the beam velocity, with the remaining spectra generated by pre-equilibrium and equilibrium processes. The double-differential cross sections are fitted with a moving-source parametrization. Also reported are the data without corrections for neutron flux attenuation in the target and other intervening materials and for neutron production in nontarget materials near the target position. These uncorrected spectra are compared with SHIELD-HIT and PHITS transport model calculations. The transport model calculations reproduce the spectral shapes well but, on average, underestimate the magnitudes of the cross sections.

DOI： 10.1103/PhysRevC.73.024603

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DOI： 10.1088/1742-6596/49/1/033

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Other Link： http://orcid.org/0000-0001-8864-369X

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Language：English   Publishing type：Research paper (bulletin of university, research institution)  

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DOI： 10.1142/9789812702739_0066

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DOI： 10.1142/9789812702739_0048

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DOI： 10.1016/j.nuclphysa.2005.05.035

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DOI： 10.1016/j.nuclphysa.2005.05.137

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DOI： 10.1088/0954-3899/31/10/023

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Excited states in 12 Be were investigated by measuring alpha-inelastic scattering of 12 Be. New excited states in Be-12 were observed at 10.9 MeV and 11.3 MeV in a decay-energy spectrum of the He-6+He-6 final channel. Spins for these levels were determined to be 0 and 2, respectively, from the angular distributions of the inelastic scattering to these excited states. The observed states may be members of the rotational band with a He-6-He-6 cluster structure.

DOI： 10.1016/j.nuclphysa.2004.04.057

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

DOI： 10.1016/j.nuclphysa.2004.03.024

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DOI： 10.1016/j.nuclphysa.2004.03.024

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMERICAN PHYSICAL SOC  

Excited states of Si-34 were studied in the H-2(Si-34, Si-34 gamma) reaction using a radioactive Si-34 beam at 38.4A MeV and a liquid deuterium target. Deexcitation gamma rays were measured using a NaI(Tl)-scintillator array in coincidence with scattered Si-34 particles. From gamma-gamma coincidence analyses, the gamma lines at 1.193, 1.715, and 2.696 MeV, which were reported previously but unplaced in the level diagram, were found to be associated with the 3.326-MeV gamma line corresponding to the transition from the first 2(+) state to the ground state. This excludes the 1.193-MeV line as a candidate for the transition from the 2(+) state to the second 0(+) state, as suggested by Nummela et al. [Phys. Rev. C 63, 044316-2001)].

DOI： 10.1103/PhysRevC.67.064315

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

An isomeric 0(+) state in Be-12 was found at E-x = 2.24 MeV The isomer was identified by measuring coincident two gamma-rays from in-flight Be-12 nuclei, Be-12m --> Be-12* (2(1)(+)) Be-12(g.s)., produced by the projectile fragmentation of O-18 at 100 A MeV on a beryllium target. Its spin was determined to be 0(+) by the angular correlation of the two gamma-rays. The low excitation energy of the 0(+) state is a strong evidence of the break of the N = 8 shell closure in the Be-12 nucleus. (C) 2003 Published by Elsevier Science B.V.

DOI： 10.1016/S0370-2693(03)00341-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Neutron capture of short-lived isotopes can be important within several astrophysical environments. The laboratory investigation of these reactions can be difficult since these isotopes cannot form a target. We used radioactive beams and measured the inverse reaction instead. Particularly we used (15)C and (9)Li beams to measure the (14)C(n,gamma)(15)C, and (8)Li(n, gamma)(9)Li reactions. We determined the reaction rates within the astrophysically interesting temperature range. Our data for the (14)C capture rises quickly up to 8mub and then it decreases by a factor of two at 1 MeV. We investigated neutron capture by 8 Li which is one possible leak of the bridging reaction (8)Li(alpha, n)(11)B of the A=8 gap. We found that this leak is lower than the theoretical expectations.

DOI： 10.1016/S0375-9474(03)00951-5

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DOI： 10.1016/S0375-9474(03)00826-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

An attempt was made to measure the excitation function of the cross section for the Li-8(n,gamma)Li-9 reaction by performing the inverse reaction Li-9(gamma,n)Li-8, with the equivalent photons in the electric field of nuclei in a Pb target providing the gamma rays for the reaction. The energy spectrum of lithium nuclei in coincidence with neutrons had no discernible peak where any beam-velocity Li-8's would be located. Statistically, a Gaussian-shaped Li-8 peak could have been present with 30+/-29 counts, which we interpreted as consistent with zero, with a two-standard-deviation upper limit of 87 counts. Using the fact that neutron capture on Li-8 must be dominantly s-wave capture, and applying detailed balance, we obtained, with E in eV, sigma(n,gamma)<930E(-1/2) mu b. The corresponding limit on the astrophysical reaction rate is <790 cm(3) mol(-1) s(-1). Theoretical predictions of the reaction rate have exceeded our upper limit by factors of 3-50.

DOI： 10.1103/PhysRevC.67.015806

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Publishing type：Research paper (international conference proceedings)  

Inelastic scattering of the neutron-rich nucleus 12Be on a liquid-He target has been studied by measuring de-excitation γ rays in coincidence with scattered 12Be. In the angular distribution, a difference between the 21+ and the 1- state in 12Be was cleary seen.

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Language：English   Publishing type：Research paper (other academic)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Physical Society  

We have measured the double-differential cross sections for neutron production from C, Ne, and Ar projectiles at E/A = 290-600 MeV on C, Cu, and Pb targets. Neutron energies were measured at laboratory angles between 5° and 80°. The measured neutron spectra have three components. At forward angles, a prominent peak originating from the projectile-fragmentation process was observed. The velocity of neutrons corresponding to the peak was about the same as that of the projectile. In addition to the peak, two components of Maxwellian-shape distributions corresponding to the preequilibrium and equilibrium processes were observed. By fitting with a moving-source model having three components, the neutron spectra were fairly well described. The parameters obtained for each component are consistent with a picture of the projectile fragmentation, preequilibrium, and equilibrium processes. By integrating the fitted functions with respect to the neutron energies and solid angles, the angular distributions and total cross sections for the neutron production were determined. The neutron spectra, angular distributions, and total cross sections were compared with those calculated by the quantum molecular dynamics and heavy-ion codes. We found that neither of the codes could reproduce the measured cross sections for all combinations of the projectiles and targets.

DOI： 10.1103/PhysRevC.64.054609

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Physical Society  

A new Coulomb breakup experiment was performed for 7Li with an improved experimental technique and theoretical treatment. Energy spectra of α particles and tritons were examined to find the signature of post-Coulomb acceleration in the breakup of 7Li at Eαt=0. The data revealed the delayed nature of nonresonant breakup of astrophysical relevance that stems from quantum tunneling. Semiclassical discussions are presented of the lifetime of continuum states in 7Li and distortion of relative kinetic energies between α and t by post-Coulomb acceleration. Dynamical calculations of Coulomb breakup were performed by solving a time-dependent Schrödinger equation. A simple potential model of 7Li was employed. The dynamical calculations reasonably reproduced experimental cross sections for both resonant and nonresonant breakup with two key ingredients: higher order effects and mixture of E1 and E2 multipoles. Considering the dominant role of the first-order E1 nature in adiabatic Coulomb breakup, cross sections in the vα≥vt branch at 7 °-15 ° for 64Zn and 90Zr were used to deduce astrophysical S factors S(E) for t(α, γ)7Li. They exhibit a moderate energy dependence at small energies. The strongly energy-dependent S(E) resulted from the previous Coulomb breakup experiment based on cross sections with vα≤vt
they are most likely Coulomb distorted and are revised in the present work.

DOI： 10.1103/PhysRevC.63.035801

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Physical Society  

We have measured the double-differential cross sections for neutron production from C, Ne, and Ar projectiles at E/A = 290-600 MeV on C, Cu, and Pb targets. Neutron energies were measured at laboratory angles between 5° and 80°. The measured neutron spectra have three components. At forward angles, a prominent peak originating from the projectile-fragmentation process was observed. The velocity of neutrons corresponding to the peak was about the same as that of the projectile. In addition to the peak, two components of Maxwellian-shape distributions corresponding to the preequilibrium and equilibrium processes were observed. By fitting with a moving-source model having three components, the neutron spectra were fairly well described. The parameters obtained for each component are consistent with a picture of the projectile fragmentation, preequilibrium, and equilibrium processes. By integrating the fitted functions with respect to the neutron energies and solid angles, the angular distributions and total cross sections for the neutron production were determined. The neutron spectra, angular distributions, and total cross sections were compared with those calculated by the quantum molecular dynamics and heavy-ion codes. We found that neither of the codes could reproduce the measured cross sections for all combinations of the projectiles and targets.

DOI： 10.1103/PhysRevC.64.054609

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

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

As a test for the time scale of neutron emission, two-neutron intensity interferometry was applied to the reaction Ar-40+Ho-165 at E/A = 25 MeV. After appropriate corrections for neutron scattering, the correlation function showed a lifetime that was about a factor of two shorter than the lifetime predicted for the statistical decay of an equilibrated nucleus. Preequilibrium emission may explain some of this difference. [S0556-2813(98)00210-6].

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Cross sections were measured at energies of astrophysical relevance for the non-resonant breakup of 42 MeV-Li-7 by 6 targets. It was found that post-acceleration of the alpha and the triton in the target Coulomb field is vanishingly small, independent of the target nucleus, compared to that for prompt breakup, The transition probabilities were evaluated for the astrophysical continua in Li-7 which decay by tunneling through the Coulomb barrier. They are consistent with the present observations. (C) 1998 Elsevier Science B.V.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The cross section, energy distribution and angular distribution of complex fragments emitted in the reaction Kr-84+ Al-27 at the incident energy of 10.6 MeV/nucleon were measured to study the decay mechanism of a highly excited nucleus. Through coincidence measurements between the light charged particles and the binary decay fragments it is found that the pre-scission charge multiplicity is about 80% of the total one. The experimental distributions are well reproduced by the Extended Hauser-Feshbach Method (EHFM), introducing a cut-off energy of the excitation energy of fragments E(cut-off). The fission delay time is determined to be 2 x 10(-20) seconds. The role and the physical meaning of E(cut-off) is discussed.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Physical Society  

Photodisintegration of 11Li was accomplished by sending a beam of 11Li at 28 MeV/nucleon through the equivalent photon field of a lead target. By measuring the complete kinematics of the disintegration products, 9Li+n+n, we constructed the correlation of the angle between the two neutrons in the rest frame of the 11Li. The correlation is independent of angle. This result argues against the existence of a bound dineutron in the ground state of 11Li.

DOI： 10.1103/PhysRevC.54.1589

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

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The Coulomb excitation of a very neutron-rich nucleus Mg-32 to its 2(+) State was studied using an unstable nuclear beam of Mg-32 at 49.2 MeV/u with a Pb-208 target. The B(E2) value of 454 +/- 78 e(2)fm(4) was extracted by a coupled channel analysis. The value is in good agreement with recent predictions. It confirms a large deformation for Mg-32 suggested by the low excitation energy of the 2(+) state, and points to the vanishing of the N = 20 shell gap.

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DOI： 10.1109/23.387356

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

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ADAM HILGER LTD  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

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

Angular distributions of fission fragments emitted in the 40Ar+209Bi reaction at 26 MeV u-1 were measured in coincidence with projectile-like fragments (PLF). Linear momentum transfer, angular momentum transfer ltr and spin alignment PZZ of the fissile nucleus were deduced as functions of the atomic number Z of PLF. Observed trend of ltr and PZZ suggests that a significant part of the PLF is emitted in dissipative process. Large missing momenta were observed. They are attributed to pre-equilibrium light-particle emission from the fissile nucleus.

DOI： 10.1088/0954-3899/18/2/020

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

Angular distributions of fission fragments emitted in the 40Ar+209Bi reaction at 26 MeV u-1 were measured in coincidence with projectile-like fragments (PLF). Linear momentum transfer, angular momentum transfer ltr and spin alignment PZZ of the fissile nucleus were deduced as functions of the atomic number Z of PLF. Observed trend of ltr and PZZ suggests that a significant part of the PLF is emitted in dissipative process. Large missing momenta were observed. They are attributed to pre-equilibrium light-particle emission from the fissile nucleus.

DOI： 10.1088/0954-3899/18/2/020

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

In order to investigate the evolution of the GDR from low to high excitation energies, a series of experiments, in which high energy γ-rays were measured in heavy ion fusion reactions, have been performed at JAFRI and at RIKEN. It has been confirmed that the width of the GDR increases rapidly for Ex ≥ 100 MeV and our previously introduced Γ(Ex) can explain the data well for 80 ≤ Ex ≤ 120 MeV. The limiting temperature of the nucleus for existing of the GDR has been deduced for A ∼ 70, 105 and 130. The GDR seems to disappear at the temperature of about a quarter of the resonance energy. © 1992.

DOI： 10.1016/0375-9474(92)90807-V

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AIP PRESS  

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DOI： 10.1016/0370-2693(90)90155-Y

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

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The density-dependent interaction based on the Bonn-J̈lich G-matrix NN interaction was used in a distorted-wave Born approximation analysis of (p,p) and (p,n) data for p-shell nuclei at Ep=35 MeV. Calculations with this interaction fit the data as well as the commonly used density-independent interaction M3Y and gave significant improvement for analyzing powers of unnatural-parity transitions. Most of the improvement was found to be due to the tensor part of the interaction. © 1990 The American Physical Society.

DOI： 10.1103/PhysRevC.42.457

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.58.2.1.0_22_4

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.58.1.1.0_46_4

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Language：Japanese   Publisher：一般社団法人 日本物理学会  

DOI： 10.11316/jpsgaiyo.57.1.1.0_35_1

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Language：Japanese   Publisher：一般社団法人 日本物理学会  

DOI： 10.11316/jpsgaiyo.57.1.1.0_42_2

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