Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Yuichi Ichikawa Last modified date:2021.06.15

Associate Professor / Department of Physics / Faculty of Sciences


Papers
1. Y. Ichikawa, Nuclear-moment Measurement of Exotic Nuclei Using Spin-oriented Beams at RIBF, AIP Conference Proceedings, 10.1063/5.0039413, 2319, 080021, 2021.02.
2. Y. Ichikawa, H. Nishibata, Y. Tsunoda, A. Takamine, K. Imamura, T. Fujita, T. Sato, S. Momiyama, Y. Shimizu, D. S. Ahn, K. Asahi, H. Baba, D. L. Balabanski, F. Boulay, J. M. Daugas, T. Egami, N. Fukuda, C. Funayama, T. Furukawa, G. Georgiev, A. Gladkov, N. Inabe, Y. Ishibashi, T. Kawaguchi, T. Kawamura, Y. Kobayashi, S. Kojima, A. Kusoglu, I. Mukul, M. Niikura, T. Nishizaka, A. Odahara, Y. Ohtomo, T. Otsuka, D. Ralet, G. S. Simpson, T. Sumikama, H. Suzuki, H. Takeda, L. C. Tao, Y. Togano, D. Tominaga, H. Ueno, H. Yamazaki, X. F. Yang, Magnetic moment of the isomeric state of 75Cu measured with a highly spin-aligned beam, JPS Conference Proceedings, 10.7566/JPSCP.32.010047, 32, 010047, 2020.07.
3. Y. Ichikawa, H. Nishibata, Y. Tsunoda, A. Takamine, K. Imamura, T. Fujita, T. Sato, S. Momiyama, Y. Shimizu, D. S. Ahn, K. Asahi, H. Baba, D. L. Balabanski, F. Boulay, J. M. Daugas, T. Egami, N. Fukuda, C. Funayama, T. Furukawa, G. Georgiev, A. Gladkov, N. Inabe, Y. Ishibashi, T. Kawaguchi, T. Kawamura, Y. Kobayashi, S. Kojima, A. Kusoglu, I. Mukul, M. Niikura, T. Nishizaka, A. Odahara, Y. Ohtomo, T. Otsuka, D. Ralet, G. S. Simpson, T. Sumikama, H. Suzuki, H. Takeda, L. C. Tao, Y. Togano, D. Tominaga, H. Ueno, H. Yamazaki, X. F. Yang, Interplay between nuclear shell evolution and shape deformation revealed by the magnetic moment of 75Cu, Nature Physics, 10.1038/s41567-018-0410-7, 15, 4, 321-325, 2019.04, Exotic nuclei are characterized by having a number of neutrons (or protons) in excess relative to stable nuclei. Their shell structure, which represents single-particle motion in a nucleus may vary due to nuclear force and excess neutrons, in a phenomenon called shell evolution. This effect could be counterbalanced by collective modes causing deformations of the nuclear surface. Here, we study the interplay between shell evolution and shape deformation by focusing on the magnetic moment of an isomeric state of the neutron-rich nucleus 75Cu. We measure the magnetic moment using highly spin-controlled rare-isotope beams and achieve large spin alignment via a two-step reaction scheme that incorporates an angular-momentum-selecting nucleon removal. By combining our experiments with numerical simulations of many-fermion correlations, we find that the low-lying states in 75Cu are, to a large extent, of single-particle nature on top of a correlated 74Ni core. We elucidate the crucial role of shell evolution even in the presence of the collective mode, and within the same framework we consider whether and how the double magicity of the 78Ni nucleus is restored, which is also of keen interest from the perspective of nucleosynthesis in explosive stellar processes..
4. Kei Imamura, Yukari Matsuo, Wataru Kobayashi, Tsuyoshi Egami, Makoto Sanjo, Aiko Takamine, Tomomi Fujita, Daiki Tominaga, Yutaro Nakamura, Takeshi Furukawa, Takashi Wakui, Yuichi Ichikawa, Hiroki Nishibata, Tomoya Sato, Aleksey Gladkov, Long Chun Tao, Takafumi Kawaguchi, Yosuke Baba, Mari Iijima, Haruka Gonda, Yasuharu Takeuchi, Rio Nakazato, Hitoshi Odashima, Hideki Ueno, Absolute optical absorption cross-section measurement of Rb atoms injected into superfluid helium using energetic ion beams, Applied Physics Express, 10.7567/1882-0786/aaf0a9, 12, 1, 2019.01, We report on a new in situ laser spectroscopy technique using superfluid helium and a highly energetic ion beam. In taking advantage of superfluid helium as a host matrix for laser spectroscopy, we were able to develop an extremely low background detection system. The first demonstration using 85 Rb 31+ ion beam (66 MeV/nucleon) accelerated at the RIKEN accelerator facility shows improvement of detection limit by two orders of magnitude. A quantitative evaluation of Rb atoms in the observation region enables an analysis of their optical absorption cross-section in superfluid helium from the fluorescence intensity dependence on ion-beam intensity and applied laser power..
5. Shinji Kinbara, Hiroyuki Ekawa, Tomomi Fujita, Shuhei Hayakawa, Sanghoon Hwang, Yuichi Ichikawa, Kei Imamura, Rina Murai, Myint Kyaw Soe, May Sweet, Aiko Takamine, Aye Moh Moh Theint, Hideki Ueno, Junya Yoshida, Masahiro Yoshimoto, Kazuma Nakazawa, Charge identification of low-energy particles for double-strangeness nuclei in nuclear emulsion, Progress of Theoretical and Experimental Physics, 10.1093/ptep/pty137, 2019, 1, 2019.01, A development has been achieved in the identification method of the charges 1 to 5 of nuclides from the decay of double hypernuclei to be uniquely recognized by their nuclear species. The method is basically the measurement of track volume by the widths, depths, and angles of tracks of exposed nuclei of 1 H, 4 He, 7 Li, 9 Be, and 11 B in nuclear emulsion at RIken Projectile-fragment Separator of RIKEN Radioactive Isotope Beam Factory. After their calibration by α particles, we obtained a quadric function to present a unified recognition of tracks with volume ratios of five nuclei to the α particles. The function in the emulsion has been applied to a candidate event of a Ξ hypernucleus for identification of the production and decay processes. We succeeded in recognizing a daughter nuclear fragment of a single-Λ hypernucleus as 6 He with a likelihood ratio of 0.9; the process was then uniquely identified as Ξ + 14 N → Λ 9 Be + Λ 5 He + n..
6. Long Chun Tao, Y. Ichikawa, Cen Xi Yuan, Y. Ishibashi, A. Takamine, A. Gladkov, T. Fujita, K. Asahi, T. Egami, C. Funayama, K. Imamura, Jian Ling Lou, T. Kawaguchi, T. Nishizaka, T. Sato, D. Tominaga, Xiao Fei Yang, H. Yamazaki, Yan Lin Ye, H. Ueno, Negative Parity States in 39Cl Configured by Crossing Major Shell Orbits, Chinese Physics Letters, 10.1088/0256-307X/36/6/062101, 36, 6, 2019.01, Traditional "magic numbers" were once regarded as immutable throughout the nuclear chart. However, unexpected changes were found for unstable nuclei around N = 20. With both proton and neutron numbers around the magic number of 20, the neutron-rich 39Cl isotope provides a good test case for the study of the quantumstate evolution across the major shell. In the present work, the negative parity states in 39Cl are investigated through the β decay spectroscopy of 39S. Newly observed γ transitions together with a new state are assigned into the level scheme of 39Cl. The spin parity of 5/2- for the lowest negative parity state in 39Cl is reconfirmed using the combined γ transition information. These systematic observations of the negative parity states in 39Cl allow a comprehensive comparison with the theoretical descriptions. The lowest 5/2- state in 39Cl remains exotic in terms of comparisons with existing theoretical calculations and with the neighboring isotopes having similar single-particle configurations. Further experimental and theoretical investigations are suggested..
7. T. Sato, Y. Ichikawa, S. Kojima, C. Funayama, S. Tanaka, T. Inoue, A. Uchiyama, A. Gladkov, A. Takamine, Y. Sakamoto, Y. Ohtomo, C. Hirao, M. Chikamori, E. Hikota, T. Suzuki, M. Tsuchiya, T. Furukawa, A. Yoshimi, C. P. Bidinosti, T. Ino, H. Ueno, Y. Matsuo, T. Fukuyama, N. Yoshinaga, Y. Sakemi, K. Asahi, Development of co-located 129Xe and 131Xe nuclear spin masers with external feedback scheme, Physics Letters, Section A: General, Atomic and Solid State Physics, 10.1016/j.physleta.2017.12.003, 382, 8, 588-594, 2018.02, We report on the operation of co-located 129Xe and 131Xe nuclear spin masers with an external feedback scheme, and discuss the use of 131Xe as a comagnetometer in measurements of the 129Xe spin precession frequency. By applying a correction based on the observed change in the 131Xe frequency, the frequency instability due to magnetic field and cell temperature drifts are eliminated by two orders of magnitude. The frequency precision of 6.2 μHz is obtained for a 104 s averaging time, suggesting the possibility of future improvement to ≈ 1 nHz by improving the signal-to-noise ratio of the observation..
8. H. Heylen, M. De Rydt, G. Neyens, M. L. Bissell, L. Caceres, R. Chevrier, J. M. Daugas, Y. Ichikawa, Y. Ishibashi, O. Kamalou, T. J. Mertzimekis, P. Morel, J. Papuga, A. Poves, M. M. Rajabali, C. Stödel, J. C. Thomas, H. Ueno, Y. Utsuno, N. Yoshida, A. Yoshimi, High-precision quadrupole moment reveals significant intruder component in Al20 1333 ground state, Physical Review C, 10.1103/PhysRevC.94.034312, 94, 3, 2016.09, The electric quadrupole moment of the Al201333 ground state, located at the border of the island of inversion, was obtained using continuous-beam β-detected nuclear quadrupole resonance (β-NQR). From the measured quadrupole coupling constant νQ=2.31(4) MHz in an α-Al2O3 crystal, a precise value for the electric quadrupole moment is extracted: QsAl33=141(3) mb. A comparison with large-scale shell model calculations shows that Al33 has at least 50% intruder configurations in the ground state wave function, favoring the excitation of two neutrons across the N=20 shell gap. Al33 therefore clearly marks the gradual transition north of the deformed Na and Mg nuclei towards the normal Z≥14 isotopes..
9. Takeshi Inoue, Takeshi Furukawa, Akihiro Yoshimi, Tsubasa Nanao, Masatoshi Chikamori, Kunifumi Suzuki, Hironori Hayashi, Hirokazu Miyatake, Yuichi Ichikawa, Masato Tsuchiya, Naoto Hatakeyama, Sota Kagami, Makoto Uchida, Hideki Ueno, Yukari Matsuo, Takeshi Fukuyama, Koichiro Asahi, Frequency characteristics of nuclear spin oscillator with an artificial feedback toward search for 129Xe atomic electric dipole moment, European Physical Journal D, 10.1140/epjd/e2016-70034-8, 70, 6, 2016.06, Abstract: A 129Xe nuclearspin oscillator with an artificial feedback was constructed, and detailed studies wereconducted on its performance, focusing on the frequency stability. As a result, the majorsources of drift of the precession frequency in the present spin oscillator setup wereidentified to be drifts of a solenoid current and an environmental magnetic field. Byintroducing stabilization systems for the current and the environmental field, whichyielded improvements by one order of magnitude on the solenoid current and by a factor ofthree on the environmental field, a frequency precision of 7.9 nHz was obtained for aone-shot measurement of 3 ×104s duration. We found, however, that the Allan deviationleveled off at around 30 μHz, indicating a strong need for the precisionmonitor of the experimental conditions represented by magnetometry. The frequencystability of the spin oscillator is discussed in relation to an experimental search for anelectric dipole moment of the 129Xe atom. Graphical abstract: [Figure not available: see fulltext.].
10. A. Takamine, M. Wada, K. Okada, Y. Ito, P. Schury, F. Arai, I. Katayama, K. Imamura, Y. Ichikawa, H. Ueno, H. Wollnik, H. A. Schuessler, Towards high precision measurements of nuclear g-factors for the Be isotopes, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, 10.1016/j.nimb.2015.12.027, 376, 307-310, 2016.06, We describe the present status of future high-precision measurements of nuclear g-factors utilizing laser-microwave double and laser-microwave-rf triple resonance methods for online-trapped, laser-cooled radioactive beryllium isotope ions. These methods have applicability to other suitably chosen isotopes and for beryllium show promise in deducing the hyperfine anomaly of 11Be with a sufficiently high precision to study the nuclear magnetization distribution of this one-neutron halo nucleus in a nuclear-model-independent manner..
11. A. Kusoglu, G. Georgiev, C. Sotty, D. L. Balabanski, A. Goasduff, Y. Ishii, Y. Abe, K. Asahi, M. Bostan, R. Chevrier, M. Chikamori, J. M. Daugas, T. Furukawa, H. Nishibata, Y. Ichikawa, Y. Ishibashi, R. Lozeva, H. Miyatake, D. Nagae, T. Nanao, M. Niikura, T. Niwa, S. Okada, A. Ozawa, Y. Saito, H. Shirai, H. Ueno, D. T. Yordanov, N. Yoshida, Magnetic moment of the 13/2+ isomeric state in Cu 69
Spin alignment in the one-nucleon removal reaction, Physical Review C, 10.1103/PhysRevC.93.054313, 93, 5, 2016.05, We report on a new measurement of the g factor of the (13/2+) isomeric state in the neutron-rich nucleus Cu69. This study demonstrates the possibility of obtaining considerable nuclear spin alignment for multi-quasiparticle states in single-nucleon removal reactions. The time-dependent perturbed angular distribution (TDPAD) method was used to extract the gyromagnetic factor of the (13/2+) [T1/2=351(14) ns] isomeric state of Cu69. Its g factor was obtained as g(13/2+)=0.248(9). The experimentally observed spin alignment for the state of interest was deduced as A=-3.3(9)%..
12. Tomoya Sato, Yuichi Ichikawa, Koichiro Asahi, Shuichiro Kojima, Chikako Funayama, Shunya Tanaka, Yu Sakamoto, Yuichi Ohtomo, Chika Hirao, Masatoshi Chikamori, Eri Hikota, Takeshi Furukawa, Akihiro Yoshimi, Christopher P. Bidinosti, Takashi Ino, Hideki Ueno, Yukari Matsuo, Takeshi Fukuyama, Development Of 131Xe Co-magnetometry For Xe Atomic EDM Search, 26th International Nuclear Physics Conference, INPC 2016 Proceedings of Science, 2016-September, 2016.01, Co-magnetometry enables the elimination of systematic errors arising from the long-term drift in the magnetic field, and is essential for a precision measurement of spin precession frequency in experiments searching for electric dipole moment (EDM). 131Xe nuclear spin maser shows great promise as a co-magnetometer in a Xe EDM experiment, because the systematic error originating from the Xe-Rb interaction, which virtually limits the sensitivity in a case of a 3He co-magnetometer, will be cancelled out. The performance of a cell which contains both 129Xe and 131Xe was investigated. In the best cell among those fabricated this time, the signal-to-noise ratio in a free induction decay experiment turned out to be large enough for the operation as co-existing 129Xe-131Xe masers..
13. C. Funayama, T. Furukawa, T. Sato, Y. Ichikawa, Y. Ohtomo, Y. Sakamoto, S. Kojima, T. Suzuki, C. Hirao, M. Chikamori, E. Hikota, M. Tsuchiya, A. Yoshimi, C. P. Bidinosti, T. Ino, H. Ueno, Y. Matsuo, T. Fukuyama, K. Asahi, Performance assessment of a new laser system for efficient spin exchange optical pumping in a spin maser measurement of 129Xe EDM, Hyperfine Interactions, 10.1007/s10751-015-1203-3, 236, 1-3, 59-64, 2015.11, We demonstrate spin-exchange optical pumping of 129Xe atoms with our newly made laser system. The new laser system was prepared to provide higher laser power required for the stable operation of spin maser oscillations in the 129Xe EDM experiment. We studied the optimum cell temperature and pumping laser power to improve the degree of 129Xe spin polarization. The best performance was achieved at the cell temperature of 100 C with the presently available laser power of 1 W. The results show that a more intense laser is required for further improvement of the spin polarization at higher cell temperatures in our experiment..
14. Y. Sakamoto, C. P. Bidinosti, Y. Ichikawa, T. Sato, Y. Ohtomo, S. Kojima, C. Funayama, T. Suzuki, M. Tsuchiya, T. Furukawa, A. Yoshimi, T. Ino, H. Ueno, Y. Matsuo, T. Fukuyama, K. Asahi, Development of high-homogeneity magnetic field coil for 129Xe EDM experiment, Hyperfine Interactions, 10.1007/s10751-014-1109-5, 230, 1-3, 141-146, 2015.04, We search for 129Xe EDM by using an active nuclear spin maser. In this experiment, the amplitude of the maser oscillation signal is one of the most important parameters that eventually determine the frequency precision. The amplitude is proportional to the ratio of the transverse spin relaxation time T2 to the effective longitudinal spin relaxation time (Formula presented.). In particular, for a spin maser of 3He (a co-magnetometer) for which (Formula presented.) typically reaches ∼50 h, a long T2 is needed. T2 depends on the homogeneity of the magnetic field which is applied with coils in order to keep the spins under precession. In the present report, we discuss on the design and construction of a new coil which provided a root-mean square (rms) field gradient of less than 5.0 μG/cm. The result of the field measurement has shown that the field gradient in the cell fulfills the target condition (Formula presented.), and in fact T2 of 3He has been measured to be as long as 11,000 s..
15. T. Sato, Y. Ichikawa, Y. Ohtomo, Y. Sakamoto, S. Kojima, C. Funayama, T. Suzuki, M. Chikamori, E. Hikota, M. Tsuchiya, T. Furukawa, A. Yoshimi, C. P. Bidinosti, T. Ino, H. Ueno, Y. Matsuo, T. Fukuyama, K. Asahi, EDM measurement in 129Xe atom using dual active feedback nuclear spin maser, Hyperfine Interactions, 10.1007/s10751-014-1113-9, 230, 1-3, 147-153, 2015.04, The technique of an active nuclear spin maser is adopted in the search for electric dipole moment in a diamagnetic atom 129Xe. In order to reduce systematic uncertainties arising from long-term drifts of the external magnetic field and from the contact interaction between longitudinal polarized Rb atoms and 129Xe spin, a 3He comagnetometer with a double-cell geometry was employed. The remaining shift, which turned out to show some correlation with the cell temperature, was mitigated by stabilizing the cell temperature. As a result, the frequency drift of the 129Xe maser was reduced from 12 mHz to 700 μHz, and the determination precision of frequency of 8.7 nHz was obtained for a 2×104 s measurement time using the double-cell geometry cell..
16. Hideki Ueno, Yuichi Ichikawa, Spin-Aligned Radioactive Isotope Beams via Two-Step Fragmentation Reaction, Nuclear Physics News, 10.1080/10619127.2015.1006503, 25, 2, 12-16, 2015.04, Recently the “dispersion-matching two-step projectile-fragmentation (PF) method” has been developed as a new spin manipulation technique for a quantum system called a radioactive isotope (RI) beam [1]. This method obtains an RI beam with a high production yield while producing universally high spin alignment for a large variety of RIs. A proof-of-principle experiment was performed at the RIKEN RIBF facility [2]. By applying this method, it is expected that the measurement of the nuclear moment of an unstable nucleus, which was previously impossible, can be accomplished. In this article, after discussing the conventional mechanism for producing a spin orientation, the principle of the new method, demonstration experiments, evaluations based on the results of these experiments, and future prospects are described..
17. Xiaofei Yang, Takeshi Furukawa, Takashi Wakui, Tomomi Fujita, Kei Imamura, Yosuke Mitsuya, Miki Hayasaka, Yuichi Ichikawa, Yoko Ishibashi, Hazuki Shirai, Takahiro Suzuki, Yuta Ebara, Atsushi Hatakeyama, Michiharu Wada, Tetsu Sonoda, Yuta Ito, Tohru Kobayashi, Shunji Nishimura, Mizuki Kurata-Nishimura, Yosuke Kondo, Ken Ichiro Yoneda, Shigeru Kubono, Yoshimitsu Ohshiro, Hideki Ueno, Tsutomu Shinozuka, Tadashi Shimoda, Koichiro Asahi, Yukari Matsuo, Laser-radio-frequency double-resonance spectroscopy of 84-87Rb isotopes trapped in superfluid helium, Physical Review A - Atomic, Molecular, and Optical Physics, 10.1103/PhysRevA.90.052516, 90, 5, 2014.11, In this paper, we report on a laser spectroscopy measurement of 84-87Rb isotopes in superfluid helium (He ii) at 1.8 K using laser-radio-frequency double-resonance spectroscopy. Rb ion beams (>60 MeV/u) provided by the RIKEN projectile fragment separator (RIPS) were injected and trapped into He ii. The stopping position of atoms in He ii was precisely confirmed by laser spectroscopy. By optically pumping the trapped Rb isotopes, large atomic spin polarization (up to 40%) of each observed isotope in the ground state was achieved. The laser-radio-frequency double-resonance spectra were observed for stable 85,87Rb isotopes as well as for unstable isotopes 84,84m,86Rb by scanning a weak magnetic field with a fixed-frequency RF field. From the measured Zeeman splitting, nuclear spin values for 84m,84-87Rb isotopes were determined with reasonable accuracy. The number of ions injected into He ii for the resonance spectra measurement was on the order of 104 particles per second. This work may open new opportunities for the study of various particles trapped in condensed helium in several fields..
18. S. Michimasa, Y. Yanagisawa, K. Inafuku, N. Aoi, Z. Elekes, Zs Fülöp, Y. Ichikawa, N. Iwasa, K. Kurita, M. Kurokawa, T. Machida, T. Motobayashi, T. Nakamura, T. Nakabayashi, M. Notani, H. J. Ong, T. K. Onishi, H. Otsu, H. Sakurai, M. Shinohara, T. Sumikama, S. Takeuchi, K. Tanaka, Y. Togano, K. Yamada, M. Yamaguchi, K. Yoneda, Quadrupole collectivity in island-of-inversion nuclei 28,30Ne and 34,36Mg, Physical Review C - Nuclear Physics, 10.1103/PhysRevC.89.054307, 89, 5, 2014.05, The quadrupole collectivity of neutron-rich even-even neon and magnesium nuclei around N=20, 28,30Ne, and 32,34,36Mg, was studied via proton inelastic scattering on a liquid hydrogen target by in-beam γ-ray spectroscopy in inverse kinematics. The angle-integrated cross sections for the first 2+ states of these nuclei were determined by measuring de-excitation γ rays. The deformation lengths were extracted from the angle-integrated cross sections using distorted-wave calculations. The deformation length of 30Ne (δ(p,p′)=1.59-0.09+0.08 fm) is smaller than that of 32Mg (1.83-0.11+0.10 fm), which exhibits the largest quadrupole collectivity among the neutron-rich N=20 isotones. Along the magnesium isotopic chain, the deformation lengths of 34Mg and 36Mg were deduced to be 2.30-0.10+0.09 fm and 1.90-0.17+0.16 fm, respectively. The evolution of quadrupole deformation in the vicinity of 32Mg is discussed by comparing the present results with the theoretical calculations..
19. E. Hikota, M. Chikamori, Y. Ichikawa, Y. Ohtomo, Y. Sakamoto, T. Suzuki, C. P. Bidinosti, T. Inoue, T. Furukawa, A. Yoshimi, K. Suzuki, T. Nanao, H. Miyatake, M. Tsuchiya, N. Yoshida, H. Shirai, T. Ino, H. Ueno, Y. Matsuo, T. Fukuyama, K. Asahi, Active nuclear spin maser oscillation with double cell, 2013 International Nuclear Physics Conference, INPC 2013 EPJ Web of Conferences, 10.1051/epjconf/20146605005, 66, 2014.04, Uncertainty in the frequency precision of the planned experiment to search for a 129Xe atomic electric dipole moment is dominated by drifts in the frequency shift due to contact interaction of 129Xe with polarized Rb valence electrons. In order to suppress the frequency shift, a double-cell geometry has been adopted for the confinement of 129Xe gas. A new process has been identified to take part in the optical detection of spin precession. The parameters controlling the oscillation of the maser in this new double-cell arrangement were optimized. As a result, the frequency shift has been reduced by a factor of 10 or more from the former single-cell geometry..
20. X. F. Yang, T. Furukawa, T. Wakui, K. Imamura, H. Fujita, Y. Mitsuya, M. Hayasaka, Y. Ichikawa, Y. Ishibashi, H. Shirai, Y. Ebara, A. Hatakeyama, M. Wada, T. Sonoda, T. Ito, T. Kobayashi, S. Nishimura, M. Nishimura, Y. Kondo, K. Yoneda, H. Ueno, T. Shinozuka, T. Shimoda, K. Asahi, Y. Matsuo, An effective method for trapping ion beams in superfluid helium for laser spectroscopy experiments, 2013 International Nuclear Physics Conference, INPC 2013 EPJ Web of Conferences, 10.1051/epjconf/20146611041, 66, 2014.04, A novel laser spectroscopy technique -"OROCHI" (Optical Radioisotopes Observation in Condensed Helium as Ion-catcher) has been proposed. This method aimed to investigate the structure of exotic nuclei systematically by measuring nuclear spins and moments. For in-situ laser spectroscopy of atoms in He II, a method to trap atoms precisely at the observation region of laser is highly needed. In this work, a setup composed of a degrader, two plastic scintillators and a photon detection system is further tested and verified for adjusting and checking the stopping position of 84-87Rb beam. Details of the current setup, experimental results using this method are presented..
21. Y. Ichikawa, M. Chikamori, Y. Ohtomo, E. Hikota, Y. Sakamoto, T. Suzuki, C. P. Bidinosti, T. Inoue, T. Furukawa, A. Yoshimi, K. Suzuki, T. Nanao, H. Miyatake, M. Tsuchiya, N. Yoshida, H. Shirai, T. Ino, H. Ueno, Y. Matsuo, T. Fukuyama, K. Asahi, Search for electric dipole moment in 129Xe atom using active nuclear spin maser, 2013 International Nuclear Physics Conference, INPC 2013 EPJ Web of Conferences, 10.1051/epjconf/20146605007, 66, 2014.04, An experimental search for an electric dipole moment in the diamagnetic atom 129Xe is in progress through the precision measurement of spin precession frequency using an active nuclear spin maser. A 3He comagnetometer has been incorporated into the active spin maser system in order to cancel out the long-term drifts in the external magnetic field. Also, a double-cell geometry has been adopted in order to suppress the frequency shifts due to interaction with polarized Rb atoms. The first EDM measurement with the 129Xe active spin maser and the 3He comagnetometer has been conducted..
22. K. Asahi, Y. Ichikawa, M. Chikamori, Y. Ohtomo, E. Hikota, T. Suzuki, T. Inoue, T. Furukawa, A. Yoshimi, K. Suzuki, T. Nanao, H. Miyatake, M. Tsuchiya, N. Yoshida, H. Shirai, T. Ino, H. Ueno, Y. Matsuo, T. Fukuyama, Search for electric dipole moment in 129Xe atom using a nuclear spin oscillator, Physics of Particles and Nuclei, 10.1134/S1063779614010080, 45, 1, 199-201, 2014.01, We aim to measure the electric dipole moment (EDM) of a diamagnetic atom 129Xe using an optical-detection nuclear spin maser technique. The relation of EDM in a diamagnetic atom to nuclear Schiff moment and fundamental sources generating it is discussed, and the present status for the development of our experimental setup is presented..
23. X. F. Yang, T. Furukawa, T. Wakui, K. Imamura, H. Tetsuka, T. Fujita, Y. Yamaguchi, Y. Tsutsui, Y. Mitsuya, Y. Ichikawa, Y. Ishibashi, N. Yoshida, H. Shirai, Y. Ebara, M. Hayasaka, S. Arai, S. Muramoto, A. Hatakeyama, M. Wada, T. Sonoda, Y. Ito, T. Kobayashi, S. Nishimura, M. Nishimura, Y. Kondo, K. Yoneda, H. Ueno, T. Shinozuka, T. Shimoda, K. Asahi, Y. Matsuo, Control of stopping position of radioactive ion beam in superfluid helium for laser spectroscopy experiments, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, 10.1016/j.nimb.2013.07.068, 317, PART B, 599-602, 2013.12, In order to investigate the structure of exotic nuclei with extremely low yields by measuring nuclear spins and moments, a new laser spectroscopy technique - "OROCHI" (Optical Radioisotopes Observation in Condensed Helium as Ion-catcher) has been proposed in recent years. The feasibility of this technique has been demonstrated by means of a considerable amount of offline and online studies of various atoms in superfluid helium. For in-situ laser spectroscopy of atoms in He II, trapping atoms in the observation region of laser is a key step. Therefore, a method which enables us to trap accelerated atoms at a precise position in He II is highly needed for performing experiment. In this work, a technique making use of a degrader, two plastic scintillators and a photon detection system is established for checking the stopping position of beam based on the LISE++ calculation. The method has been tested and verified by on-line experiments with the 84,85,87Rb beam. Details of the experimental setup, working procedure and testing results of this method are presented..
24. Kei Imamura, Takeshi Furukawa, Takashi Wakui, Xiaofei Yang, Yasuhiro Yamaguchi, Hiroki Tetsuka, Yosuke Mitsuya, Yoshiki Tsutsui, Tomomi Fujita, Yuta Ebara, Miki Hayasaka, Shino Arai, Sosuke Muramoto, Yuichi Ichikawa, Yoko Ishibashi, Naoki Yoshida, Hazuki Shirai, Atsushi Hatakeyama, Michiharu Wada, Tetsu Sonoda, Yuta Ito, Hitoshi Odashima, Tohru Kobayashi, Hideki Ueno, Tadashi Shimoda, Koichiro Asahi, Yukari Matsuo, Development of a helium cryostat for laser spectroscopy of atoms with unstable nuclei in superfluid helium, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, 10.1016/j.nimb.2013.08.024, 317, PART B, 595-598, 2013.12, We are developing a new nuclear laser spectroscopic technique for the study of nuclear structure that can be applied to short-lived low-yield atoms with unstable nuclei. The method utilizes superfluid helium (He II) as a trapping medium for high-energy ion beams. A liquid helium cryostat with optical windows is a key apparatus for this type of experiment. We describe the design and the performance of the cryostat which is developed for the present project..
25. N. Yoshida, H. Ueno, A. Yoshimi, Y. Ishibashi, Y. Ichikawa, Y. Abe, K. Asahi, M. Chikamori, T. Fujita, T. Furukawa, E. Hikota, D. Nagae, Y. Ohtomo, Y. Saito, H. Shirai, T. Suzuki, X. F. Yang, Development of a new device control system for β-NMR experiments, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, 10.1016/j.nimb.2013.08.057, 317, PART B, 705-709, 2013.12, We have developed a device-control system of a β-NMR apparatus for the measurement of nuclear electromagnetic nuclear moments of rare isotopes. In this development, we installed fast relay switches into a high-power tank circuit in order to apply a strong oscillating magnetic field and to sweep its frequency as wide as possible. The system enables to conduct NMR frequency scans with wide frequency windows by dynamically changing the tank-circuit resonant frequency. Furthermore, logical electric-circuit modules of the data taking system were replaced by a programmable logic module. The system performance was evaluated in the β-NMR experiments conducted at the RIBF facility using 20F and 33Cl radioactive isotopes..
26. Y. Ishibashi, N. Yoshida, H. Ueno, A. Yoshimi, Y. Ichikawa, Y. Abe, K. Asahi, M. Chikamori, T. Fujita, T. Furukawa, E. Hikota, D. Nagae, Y. Ohtomo, Y. Saito, H. Shirai, T. Suzuki, X. F. Yang, N. Sakamoto, Development of an adiabatic field rotation system to measure spin polarization of unstable nuclei, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, 10.1016/j.nimb.2013.08.059, 317, PART B, 714-716, 2013.12, A system for the spin-polarization measurement of unstable nuclei has been developed, in which the alternation of nuclear spins takes place by adiabatically rotating a holding magnetic field for the preservation of spin polarization, without applying a resonant oscillating magnetic field for NMR. The performance of the system was studied with spin-polarized 20F ( = 2+,T1/2 = 11.163 s) produced in the 19F(d→,p)20→F reaction at E/A = 7 MeV at the RIKEN RIBF facility. In the measurement, the magnitude of 20F spin polarization |P(20F)|=1.6(2)% was successfully observed with the new system..
27. Takeshi Furukawa, Takashi Wakui, Xiaofei Yang, Tomomi Fujita, Kei Imamura, Yasuhiro Yamaguchi, Hiroki Tetsuka, Yoshiki Tsutsui, Yosuke Mitsuya, Yuichi Ichikawa, Yoko Ishibashi, Naoki Yoshida, Hazuki Shirai, Yuta Ebara, Miki Hayasaka, Shino Arai, Sosuke Muramoto, Atsushi Hatakeyama, Michiharu Wada, Tetsu Sonoda, Yuta Ito, Tohru Kobayashi, Shunji Nishimura, Mitsuki Nishimura, Yosuke Kondo, Ken Ichiro Yoneda, Shigeru Kubono, Yoshimitsu Ohshiro, Hideki Ueno, Tsutomu Shinozuka, Tadashi Shimoda, Koichiro Asahi, Yukari Matsuo, Novel nuclear laser spectroscopy method using superfluid helium for measurement of spins and moments of exotic nuclei, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, 10.1016/j.nimb.2013.08.023, 317, PART B, 590-594, 2013.12, We have been developing a novel nuclear laser spectroscopy method "OROCHI" for determining spins and moments of exotic radioisotopes. In this method, we use superfluid helium as a stopping material of energetic radioisotope beams and then stopped radioisotope atoms are subjected to in situ laser spectroscopy in superfluid helium. To confirm the feasibility of this method for rare radioisotopes, we carried out a test experiment using a 85Rb beam. In this experiment, we have successfully measured the Zeeman resonance signals from the 85Rb atoms stopped in superfluid helium by laser-RF double resonance spectroscopy. This method is efficient for the measurement of spins and moments of more exotic nuclei..
28. Y. Ichikawa, H. Ueno, Y. Ishii, T. Furukawa, A. Yoshimi, D. Kameda, H. Watanabe, N. Aoi, K. Asahi, D. L. Balabanski, R. Chevrier, J. M. Daugas, N. Fukuda, G. Georgiev, H. Hayashi, H. Iijima, N. Inabe, T. Inoue, M. Ishihara, T. Kubo, T. Nanao, T. Ohnishi, K. Suzuki, M. Tsuchiya, H. Takeda, M. M. Rajabali, Spin-aligned RI beams via two-step fragmentation reactions, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, 10.1016/j.nimb.2013.04.071, 317, PART B, 769-773, 2013.12, A method to produce spin-aligned rare isotope (RI) beams has been developed, where a scheme of two-step projectile fragmentation to produce the RI of interest with high spin alignment and a technique of momentum-dispersion matching are combined. Effectiveness of the present method was demonstrated in an experiment at the RIKEN RIBF, where an RI beam of 32Al with spin alignment of 8(1)% was successfully produced from a primary beam of 48Ca, via an intermediate RI of 33Al. Figure of merit of the present method was found to be more than 50 times greater than that of the conventional method employing single-step projectile fragmentation..
29. S. Sakaguchi, Y. Iseri, T. Uesaka, M. Tanifuji, N. Aoi, E. Hiyama, Y. Ichikawa, S. Ishikawa, K. Itoh, M. Itoh, H. Iwasaki, T. Kawabata, T. Kawahara, H. Kuboki, Y. Maeda, T. Nakao, H. Okamura, H. Sakai, Y. Sasamoto, M. Sasano, Y. Satou, K. Sekiguchi, K. Suda, D. Suzuki, A. Tamii, T. Wakui, K. Yako, M. Yamaguchi, Y. Yamamoto, Analyzing Power in Elastic Scattering of Polarized Protons from Neutron-rich Helium Isotopes, Few-Body Systems, 10.1007/s00601-013-0617-1, 54, 7-10, 1393-1398, 2013.08, The vector analyzing power has been measured for the elastic scattering of neutron-rich 6He from polarized protons at 71 MeV/nucleon. Two approaches based on local one-body potentials were applied to investigate the spin-orbit interaction between a proton and a 6He nucleus. An optical model analysis revealed that the spin-orbit potential for 6He is characterized by a shallow and long-ranged shape compared with the global systematics of stable nuclei. A semi-microscopic analysis with a α + n + n cluster folding model suggests that the inclusion of realistic interaction between a proton and the α core is important in describing the p-6He elastic scattering..
30. T. Inoue, T. Furukawa, A. Yoshimi, Y. Ichikawa, M. Chikamori, Y. Ohtomo, M. Tsuchiya, N. Yoshida, H. Shirai, M. Uchida, K. Suzuki, T. Nanao, H. Miyatake, H. Ueno, Y. Matsuo, T. Fukuyama, K. Asahi, Nuclear spin maser and experimental search for 129Xe atomic EDM, Hyperfine Interactions, 10.1007/s10751-012-0751-z, 220, 1-3, 59-63, 2013.02, The present status of an active spin maser which is being developed for an experimental search for 129Xe atomic electric dipole moment (EDM) is presented. In order to realize the long term stability of maser frequency, systematic effects for the spin maser operation were investigated. The correlations in the maser frequency with the solenoid current, the environmental field and the cell temperature were found. With the solenoid current and environmental field being stabilized and the cell temperature lowered, a frequency precision of 7. 9 nHz has been achieved for the maser operation..
31. S. Sakaguchi, T. Uesaka, N. Aoi, Y. Ichikawa, K. Itoh, M. Itoh, T. Kawabata, T. Kawahara, Y. Kondo, H. Kuboki, T. Nakamura, T. Nakao, Y. Nakayama, H. Sakai, Y. Sasamoto, K. Sekiguchi, T. Shimamura, Y. Shimizu, T. Wakui, Shallow and diffuse spin-orbit potential for proton elastic scattering from neutron-rich helium isotopes at 71 MeV/nucleon, Physical Review C - Nuclear Physics, 10.1103/PhysRevC.87.021601, 87, 2, 2013.02, Vector analyzing powers for proton elastic scattering from 8He at 71 MeV/nucleon have been measured using a solid polarized proton target operated in a low magnetic field of 0.1 T. The spin-orbit potential obtained from a phenomenological optical model analysis is found to be significantly shallower and more diffuse than the global systematics of stable nuclei, which is an indication that the spin-orbit potential is modified for scattering involving neutron-rich nuclei. A close similarity between the matter radius and the root-mean-square radius of the spin-orbit potential is also identified..
32. S. Momota, M. Mihara, D. Nishimura, M. Fukuda, Y. Kamisho, M. Wakabayashi, K. Matsuta, S. Suzuki, M. Nagashima, Shengyun Zhu, Daqing Yuan, Yongnan Zheng, Zuo Yi, Ping Fan, T. Izumikawa, A. Kitagawa, S. Sato, M. Kanazawa, M. Torikoshi, T. Minamisono, Y. Nakamura, K. Tashiro, A. Honma, N. Yoshida, H. Shirai, T. Ohtsubo, T. Nagatomo, H. Uenishi, K. Iwamoto, M. Yaguchi, T. Ogura, T. Ito, K. Yamamura, Y. Ichikawa, Y. Nojiri, J. R. Alonso, T. J.M. Symons, Momentum dependence of spin polarization for beta emitting nuclei produced through charge exchange reaction at intermediate energy, Hyperfine Interactions, 10.1007/s10751-012-0741-1, 220, 1-3, 53-58, 2013.01, In order to investigate the polarization process in charge exchange reactions, we observed the momentum and angular distribution as well as the nuclear polarization of a proton-rich beta-emitting nucleus, 28P (Iπ = 3+, T1/2 = 270 msec), produced through the reaction 28Si+9Be at E = 100 MeV/u, by selecting the momentum and the ejection angle. An analysis by using double Gaussian functions resolved the observed momentum distribution into two reaction components, nucleon knockout and pick-up abrasion reactions, as suggested in a previous study. The behavior of the observed angular distribution and nuclear polarization implies the influence of those two components. The momentum dependence of the observed nuclear polarization of 28P could be consistently reproduced by a simple model, in which two reaction components are considered. The present study also shows that the charge exchange reaction at intermediate energy is a useful method to produce polarized beta-emitting nuclei, especially for proton-rich nuclei..
33. Y. Ichikawa, H. Ueno, Y. Ishii, T. Furukawa, A. Yoshimi, D. Kameda, H. Watanabe, N. Aoi, K. Asahi, D. L. Balabanski, R. Chevrier, J. M. Daugas, N. Fukuda, G. Georgiev, H. Hayashi, H. Iijima, N. Inabe, T. Inoue, M. Ishihara, T. Kubo, T. Nanao, T. Ohnishi, K. Suzuki, M. Tsuchiya, H. Takeda, M. M. Rajabali, Novel method for the production of spin-aligned RI beams in projectile fragmentation reaction with the dispersion matching technique, Hyperfine Interactions, 10.1007/s10751-012-0682-8, 220, 1-3, 47-51, 2013.01, A novel method to produce spin-aligned rare-isotope (RI) beam has been developed, that is the two-step projectile fragmentation method with a technique of dispersion matching. The present method was verified in an experiment at the RIKEN RIBF, where an RI beam of 32Al with spin alignment of 8(1) % was successfully produced from a primary beam of 48Ca, with 33Al as an intermediate nucleus. Figure of merit of the present method was found to be improved by a factor larger than 50 compared with a conventional method employing single-step projectile fragmentation..
34. Yuichi Ichikawa, Hideki Ueno, Yuji Ishii, Takeshi Furukawa, Akihiro Yoshimi, Daisuke Kameda, Hiroshi Watanabe, Nori Aoi, Koichiro Asahi, Dimiter L. Balabanski, Raphaël Chevrier, Jean Michel Daugas, Naoki Fukuda, Georgi Georgiev, Hironori Hayashi, Hiroaki Iijima, Naoto Inabe, Takeshi Inoue, Masayasu Ishihara, Toshiyuki Kubo, Tsubasa Nanao, Tetsuya Ohnishi, Kunifumi Suzuki, Masato Tsuchiya, Hiroyuki Takeda, Mustafa M. Rajabali, Production of spin-controlled rare isotope beams, Nature Physics, 10.1038/nphys2457, 8, 12, 918-922, 2012.12, The degree of freedom of spin in quantum systems serves as an unparalleled laboratory where intriguing quantum physical properties can be observed, and the ability to control spin is a powerful tool in physics research. We propose a method for controlling spin in a system of rare isotopes which takes advantage of the mechanism of the projectile fragmentation reaction combined with the momentum-dispersion matching technique. The present method was verified in an experiment at the RIKEN RI Beam Factory, in which a degree of alignment of 8% was achieved for the spin of a rare isotope 32Al. The figure of merit for the present method was found to be greater than that of the conventional method by a factor of more than 50..
35. K. Shimada, H. Ueno, G. Neyens, K. Asahi, D. L. Balabanski, J. M. Daugas, M. Depuydt, M. De Rydt, L. Gaudefroy, S. Grévy, Y. Hasama, Y. Ichikawa, D. Kameda, P. Morel, T. Nagatomo, L. Perrot, C. Stodel, J. C. Thomas, Y. Utsuno, W. Vanderheijden, N. Vermeulen, P. Vingerhoets, E. Yagi, K. Yoshida, A. Yoshimi, Erosion of N=20 shell in Al 33 investigated through the ground-state electric quadrupole moment, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2012.07.030, 714, 2-5, 246-250, 2012.08, Electric quadrupole moment Q of the Al 33 ground state has been measured by means of β-NMR spectroscopy using a spin-polarized Al 33 beam produced in a projectile fragmentation reaction. The obtained Q moment, |Q exp( 33Al)|=132(16) emb, shows a significant excess from the prediction of shell model calculations within the sd shell. The result indicates sizable admixing of pf intruder configurations in the ground state, demonstrating that the N=20 shell closure certainly erodes in Al 33, a nucleus located on the border of the island of inversion. Comparison was made with predictions of the Monte Carlo shell model, and also a particle-vibration coupling model treating the neutron pairing correlations in the ground state of Al33. Again, a significant admixture of pf intruder configurations to the Al 33 ground state was needed in both theoretical approaches to explain the observed large Q..
36. A. Yoshimi, T. Inoue, T. Furukawa, T. Nanao, K. Suzuki, M. Chikamori, M. Tsuchiya, H. Hayashi, M. Uchida, N. Hatakeyama, S. Kagami, Y. Ichikawa, H. Miyatake, K. Asahi, Low-frequency 129Xe nuclear spin oscillator with optical spin detection, Physics Letters, Section A: General, Atomic and Solid State Physics, 10.1016/j.physleta.2012.04.043, 376, 24-25, 1924-1929, 2012.05, We have constructed a 129Xe nuclear spin oscillator which executes a self-sustained oscillation through an external feedback loop with optical detection of nuclear spin. The oscillator is capable of operating at frequencies much lower than the conventional nuclear spin maser. A method for efficient optical detection of spin has been developed and applied to the nuclear spin oscillator, and the frequency characteristics of the oscillator at low frequencies has been investigated. The spin oscillator was operated at frequencies 2.5-36 Hz. The frequency performance of the oscillator is discussed in relation to a planned search for an atomic electric dipole moment taking advantage of the present oscillator scheme..
37. R. Chevrier, J. M. Daugas, L. Gaudefroy, Y. Ichikawa, H. Ueno, M. Hass, H. Haas, S. Cottenier, N. Aoi, K. Asahi, D. L. Balabanski, N. Fukuda, T. Furukawa, G. Georgiev, H. Hayashi, H. Iijima, N. Inabe, T. Inoue, M. Ishihara, Y. Ishii, D. Kameda, T. Kubo, T. Nanao, G. Neyens, T. Ohnishi, M. M. Rajabali, K. Suzuki, H. Takeda, M. Tsuchiya, N. Vermeulen, H. Watanabe, A. Yoshimi, Is the 7/21-isomer state of 43S spherical?, Physical Review Letters, 10.1103/PhysRevLett.108.162501, 108, 16, 2012.04, We report on the spectroscopic quadrupole moment measurement of the 7/21- isomeric state in 43S, using the time dependent perturbed angular distribution technique at the RIKEN RIBF facility. Our value, Qs=23(3)efm2, is larger than that expected for a single-particle state. Shell model calculations using the modern SDPF-U interaction for this mass region reproduce remarkably well the measured Qs, and show that non-negligible correlations drive the isomeric state away from a purely spherical shape..
38. N. Imai, Y. Hirayama, Y. X. Watanabe, T. Teranishi, T. Hashimoto, S. Hayakawa, Y. Ichikawa, H. Ishiyama, S. C. Jeong, D. Kahl, S. Kubono, H. Miyatake, H. Ueno, H. Yamaguchi, K. Yoneda, A. Yoshimi, Isobaric analog resonances of the N=21 nucleus 35Si, Physical Review C - Nuclear Physics, 10.1103/PhysRevC.85.034313, 85, 3, 2012.03, Neutron single-particle states in the neutron-rich nucleus 35Si, which is located beside the N=20 shell breaking nucleus 32Mg, were investigated through their isobaric analog resonances. The excitation function for 34Si+p elastic scattering was measured around 0 in the laboratory frame by the thick target inverse kinematics method with a 34Si beam around 5 MeV/nucleon and a thick polyethylene target. Eight resonances were successfully observed. Angular momenta and proton and total widths of the resonances were assigned using R-matrix analysis. With the help of information of the β decay study, six isobaric analog resonances were identified. Spectroscopic factors and spin-parities of the corresponding parent states in 35Si are presented..
39. Y. Ichikawa, H. Ueno, Y. Ishii, T. Furukawa, A. Yoshimi, D. Kameda, H. Watanabe, N. Aoi, K. Asahi, D. L. Balabanski, R. Chevrier, J. M. Daugas, N. Fukuda, G. Georgiev, H. Hayashi, H. Iijima, N. Inabe, T. Inoue, M. Ishihara, T. Kubo, T. Nanao, T. Ohnishi, K. Suzuki, M. Tsuchiya, H. Takeda, M. M. Rajabali, Production of spin-aligned RI beam via two-step fragmentation with dispersion matching, Rutherford Centennial Conference on Nuclear Physics Journal of Physics: Conference Series, 10.1088/1742-6596/381/1/012090, 381, 1, 2012.01, To produce a radioactive-isotope (RI) beam with high spin alignment, we have developed a novel method, the two-step projectile-fragmentation (PF) method, that employs momentum-dispersion matching. An on-line experiment to produce 32A1 from 48Ca via 33A1 was performed at RIKEN RI Beam Factory. In the experiment, we succeeded in producing approximately 8% spin alignment in an RI beam of 32A1. In this paper, we focus on evaluating the magnitude of spin alignment realized in one-nucleon removal from 33A1..
40. S. Sakaguchi, Y. Iseri, T. Uesaka, M. Tanifuji, K. Amos, N. Aoi, Y. Hashimoto, E. Hiyama, M. Ichikawa, Y. Ichikawa, S. Ishikawa, K. Itoh, M. Itoh, H. Iwasaki, S. Karataglidis, T. Kawabata, T. Kawahara, H. Kuboki, Y. Maeda, R. Matsuo, T. Nakao, H. Okamura, H. Sakai, Y. Sasamoto, M. Sasano, Y. Satou, K. Sekiguchi, M. Shinohara, K. Suda, D. Suzuki, Y. Takahashi, A. Tamii, T. Wakui, K. Yako, M. Yamaguchi, Y. Yamamoto, Analyzing power in elastic scattering of 6He from a polarized proton target at 71 MeV/nucleon, Physical Review C - Nuclear Physics, 10.1103/PhysRevC.84.024604, 84, 2, 2011.08, The vector analyzing power has been measured for the elastic scattering of neutron-rich 6He from polarized protons at 71 MeV/nucleon making use of a newly constructed solid polarized proton target operated in a low magnetic field and at high temperature. Two approaches based on local one-body potentials were applied to investigate the spin-orbit interaction between a proton and a 6He nucleus. An optical model analysis revealed that the spin-orbit potential for 6He is characterized by a shallow and long-ranged shape compared with the global systematics of stable nuclei. A semimicroscopic analysis with an α+n+n cluster folding model suggests that the interaction between a proton and the α core is essentially important in describing the p+6He elastic scattering. The data are also compared with fully microscopic analyses using nonlocal optical potentials based on nucleon-nucleon g matrices..
41. S. Sakaguchi, T. Uesaka, T. Kawabata, T. Wakui, N. Aoi, Y. Hashimoto, Y. Ichikawa, K. Itoh, M. Itoh, H. Iwasaki, T. Kawahara, Y. Kondo, H. Kuboki, Y. Maeda, T. Nakamura, T. Nakao, Y. Nakayama, H. Okamura, H. Sakai, Y. Sasamoto, M. Sasano, Y. Satou, K. Sekiguchi, T. Shimamura, Y. Shimizu, M. Shinohara, K. Suda, D. Suzuki, Y. Takahashi, A. Tamii, K. Yako, M. Yamaguchi, Elastic scattering of neutron-rich helium isotopes from polarized protons at 71 MeV/A, International Nuclear Physics Conference 2010, INPC2010 Journal of Physics: Conference Series, 10.1088/1742-6596/312/8/082037, 312, SECTION 8, 2011.01, The vector analyzing power has been measured for the elastic scattering of neutron-rich 6He and 8He from polarized protons at 71 MeV/A making use of a newly constructed solid polarized proton target operated in a low magnetic field of 0.1 T and at a relatively high temperature of 100 K. An optical model analysis revealed that the spin-orbit potentials for 6He and 8He are characterized by shallow and long-ranged shape compared with the global systematics of stable nuclei. Such a characteristics reflect a diffused density distribution of the neutron-rich isotopes..
42. T. Furukawa, T. Wakui, A. Sasaki, S. Izumi, Y. Ichikawa, A. Yoshimi, K. Tajiri, Y. Ishii, N. Yoshida, Y. Matsuura, Y. Kato, Y. Yamaguchi, K. Imamura, M. Makuta, A. Hatakeyama, M. Wada, T. Sonoda, Y. Ito, T. Nanao, T. Kobayashi, S. Nishimura, M. Nishimura, Y. Kondo, N. Aoi, K. Yoneda, S. Kubono, Y. Ohshiro, H. Ueno, T. Shimoda, T. Shinozuka, K. Asahi, Y. Matsuo, Photon detection from stopped 87Rb atoms injected into superfluid helium for a new nuclear laser spectroscopy of rare radioisotopes, Journal of Physics: Conference Series, 10.1088/1742-6596/302/1/012054, 302, 1, 2011.01, We have been developing a new nuclear laser spectroscopic method "OROCHI" for determining spins and moments of exotic RIs. This is a method based on the combination of superfluid helium as a stopper of radioactive isotope (RI) beam and in-situ laser spectroscopy of RI atoms. This unique method will enable us to measure nuclear spins and electromagnetic moments of extremely low yield RI (less than 1 particle per second). To confirm the feasibility of this method for rare radioisotopes, we carried out the first on-line experiment with a 87Rb beam, aiming at evaluating the minimum beam intensity required for the measurement. The LIF (Laser Induced Fluorescence) photons from the 87Rb atoms stopped in He II are successfully observed in the on-line experiment. The obtained LIF intensity is nearly consistent with the intensity calculated from the photo-absorption cross section of atoms in He II..
43. K. Matsuta, D. Nishimura, M. Fukuda, Y. Fujita, M. Mihara, E. Ganioǧlu, G. Susoy, Y. Ichikawa, S. Momota, A. Kitagawa, M. Kanazawa, M. Torikoshi, S. Sato, B. Rubio, Precise branching ratio of 24mAl beta decay, International Nuclear Physics Conference 2010, INPC2010 Journal of Physics: Conference Series, 10.1088/1742-6596/312/9/092039, 312, SECTION 9, 2011.01, The branching ratio of the isomeric γ decay of 24mAl has been measured to be 69.6(7)% which is much smaller than the previously accepted value of 82.5(30)%. As a result, the branching ratio to the 24Mg ground state increases up to 24.1(7)% assuming that the other β-decay branching ratios are the previously accepted values. The half-life of 24mAl was also precisely determined to be 130.9(13) ms. The B(GT) value from the ground state of 24Mg to the 24mAl of 0.0577(16) deduced from the β decay is now in good agreement with that deduced from charge-exchange reactions..
44. Y. Ichikawa, T. K. Onishi, D. Suzuki, H. Iwasaki, T. Kubo, V. Naik, A. Chakrabarti, N. Aoi, B. A. Brown, N. Fukuda, S. Kubono, T. Motobayashi, T. Nakabayashi, T. Nakamura, T. Nakao, T. Okumura, H. J. Ong, H. Suzuki, M. K. Suzuki, T. Teranishi, K. N. Yamada, H. Yamaguchi, H. Sakurai, Proton-rich nuclear structure and mirror asymmetry investigated by β-decay spectroscopy of 24Si, International Nuclear Physics Conference 2010, INPC2010 Journal of Physics: Conference Series, 10.1088/1742-6596/312/9/092031, 312, SECTION 9, 2011.01, In order to investigate the characteristic properties of proton-rich nuclei, β-decay spectroscopy was carried out on 24Si. The Gamow-Teller transition strength B(GT) of 24Si to low-lying states in 24Al was determined. Considering in particular the breaking of mirror symmetry for energy levels and B(GT), we discuss the behavior of a weakly-bound s-orbital proton by incorporating a recent experimental result..
45. M. Mihara, T. Izumikawa, H. Ueno, K. Matsuta, D. Nishimura, T. Nagatomo, T. Moriguchi, Y. Ito, D. Nagae, M. Fukuda, A. Yoshimi, K. Yamada, M. Takechi, Y. Ichikawa, S. Momota, Y. Hirayama, T. Ohtsubo, S. Suzuki, T. Kubo, Y. Namiki, A. Ozawa, Y. Ishibashi, H. Oishi, K. Suzuki, I. Hachiuma, K. Namihira, D. Horikawa, T. Minamisono, T. Yamaguchi, T. Kuboki, T. Suzuki, K. Satoh, Y. Kobayashi, K. Asahi, K. Matsukawa, K. Shirai, Beta-NMR measurement of 58Cu in Si, Hyperfine Interactions, 10.1007/s10751-010-0249-5, 197, 1, 143-147, 2010.12, The β-NMR study of short-lived nucleus 58Cu (Iπ = 1+, T1/2 = 3.2 s) in Si has been performed. Spin polarization of 58Cu induced by the charge exchange reaction of 58Ni was observed in Si at 15 K. The 58Cu magnetic moment {pipe}μ[58Cu]{pipe} = (0.46±0.03)μN deduced from the β-NMR spectrum is consistent with the previous results on the laser spectroscopy. The present result shows that the 58Cu nucleus is promising as a new nuclear probe for the microscopic study of Cu impurities in Si..
46. T. Nagatomo, H. Ueno, M. Mihara, K. Matsuta, A. Yoshimi, Y. Ichikawa, K. Yamada, H. Kawamura, A. Ozawa, T. Moriguchi, Y. Ishibashi, K. Asahi, M. Uchida, K. Suzuki, T. Inoue, Y. Hasama, H. Iijima, T. Sumikama, M. Fukuda, T. Minamisono, Precise nuclear moments of extremely proton-rich nuclus 23Al, Hyperfine Interactions, 10.1007/s10751-010-0262-8, 198, 1, 103-107, 2010.12, Electric quadrupole coupling constant eqQ/h of the extremely proton-rich 23Al (Iπ = 5/2+, T1/2 = 0.47 s) nucleus implanted into an Al2O3 single crystal has been measured for the first time, using the β-ray detecting nuclear quadrupole resonance method (β-NQR) in a high magnetic field. As a preliminary result, the quadrupole coupling constant was determined as {pipe}eqQ/h(23Al) {pipe} = 2.66±0.77 MHz. Using the quadrupole coupling constant of 27Al in Al2O3 as a reference, the Q moment of the ground state of 23Al was extracted as {pipe}Q(23Al){pipe} ~ 160 mb, which is well explained by the shell model calculation in the sd-shell model space with the USD interaction..
47. T. Uesaka, S. Sakaguchi, Y. Iseri, K. Amos, N. Aoi, Y. Hashimoto, E. Hiyama, M. Ichikawa, Y. Ichikawa, S. Ishikawa, K. Itoh, M. Itoh, H. Iwasaki, S. Karataglidis, T. Kawabata, T. Kawahara, H. Kuboki, Y. Maeda, R. Matsuo, T. Nakao, H. Okamura, H. Sakai, Y. Sasamoto, M. Sasano, Y. Satou, K. Sekiguchi, M. Shinohara, K. Suda, D. Suzuki, Y. Takahashi, M. Tanifuji, A. Tamii, T. Wakui, K. Yako, Y. Yamamoto, M. Yamaguchi, Analyzing power for proton elastic scattering from the neutron-rich He6 nucleus, Physical Review C - Nuclear Physics, 10.1103/PhysRevC.82.021602, 82, 2, 2010.08, Vector analyzing power for the proton-He6 elastic scattering at 71 MeV/nucleon has been measured for the first time, with a newly developed polarized proton solid target, which works at a low magnetic field of 0.09 T. The results are found to be incompatible with a t-matrix folding model prediction. Comparisons of the data with g-matrix folding analyses clearly show that the vector analyzing power is sensitive to the nuclear structure model used in the reaction analysis. The α-core distribution in He6 is suggested to be a possible key for understanding the nuclear structure sensitivity..
48. Y. Ichikawa, T. K. Onishi, D. Suzuki, H. Iwasaki, T. Kubo, V. Naik, A. Chakrabarti, N. Aoi, B. A. Brown, N. Fukuda, S. Kubono, T. Motobayashi, T. Nakabayashi, T. Nakamura, T. Nakao, T. Okumura, H. J. Ong, H. Suzuki, M. K. Suzuki, T. Teranishi, K. N. Yamada, H. Yamaguchi, H. Sakurai, Gamow-Teller transition of the proton-rich nucleus 24Si, 7th Japan-China Joint Nuclear Physics Symposium Nuclear Physics Trends - 7th China-Japan Joint Nuclear Physics Symposium, 10.1063/1.3442606, 265-269, 2010.07, The Gamow-Teller transition strength B(GT) of 24Si was measured to investigate characteristic structure of proton-rich nuclei induced by a weakly-bound proton. By combining the results of the delayed γ-ray and proton measurements, the entire decay scheme of 24Si was reconstructed, then the B(GT) of 24Si was deduced. Focusing to the low-lying states, the B(GT) of 24Si to the 11+ and 12+ states in 24Al were smaller than that of the mirror nucleus 24Ne by 22 % and 10 %, respectively. The mirror asymmetry of B(GT) indicates the configuration change in the wave function. Through the comparison with theoretical shell-model calculations, it is implied that the configuration change is attributed to the lowering of the 1s 1/2 orbital. The applicability of the theoretical calculations was checked using overall B(GT) distribution..
49. Y. Ichikawa, T. K. Onishi, D. Suzuki, H. Iwasaki, T. Kubo, V. Naik, A. Chakrabarti, N. Aoi, B. A. Brown, N. Fukuda, S. Kubono, T. Motobayashi, T. Nakabayashi, T. Nakamura, T. Nakao, T. Okumura, H. J. Ong, H. Suzuki, M. K. Suzuki, T. Teranishi, K. N. Yamada, H. Yamaguchi, H. Sakurai, Mirror asymmetry for B(GT) of 24Si induced by Thomas-Ehrman shift, 7th Tours Symposium on Nuclear Physics and Astrophysics Tours Symposium on Nuclear Physics and Astrophysics - VII, 10.1063/1.3455953, 290-293, 2010.07, We carried out the β-decay spectroscopy on 24Si in order to investigate a change in configuration in the wave function induced by Thomas-Ehrman shift from a perspective of mirror asymmetry of B(GT). We observed two βtransitions to low-lying bound states in 24Al for the first time. In this proceeding, the B(GT) of 24Si is compared with that of the mirror nucleus 24Ne, and the mirror asymmetry of B(GT) is determined. Then the origin of the B(GT) asymmetry is discussed through the comparison with theoretical calculations..
50. Yuichi Ichikawa, Mirror asymmetry investigated by β decay of proton-rich 24Si, Modern Physics Letters A, 10.1142/S0217732310000587, 25, 21-23, 1895-1898, 2010.07, The β-decay spectroscopy on 24Si was carried out in order to investigate characteristic properties of proton-rich nuclei from a perspective of mirror asymmetry. We observed two β transitions to low-lying bound states in 24Al for the first time. The B(GT) of 24Si were deduced to be 0.13(2) and 0.14(2), which were smaller than those of the mirror transition by 22(11)% and 10(8)%, respectively. Through the comparison with theoretical calculations taking into account the Coulomb force and the Thomas-Ehrman shift, the mirror asymmetry of B(GT) is attributed to the lowering of the proton 1s1/2 orbital..
51. D. Suzuki, T. Sumikama, M. Ogura, W. Mittig, A. Shiraki, Y. Ichikawa, H. Kimura, H. Otsu, H. Sakurai, Y. Nakai, M. S. Hussein, Resonant neutrino scattering
An impossible experiment?, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2010.03.024, 687, 2-3, 144-148, 2010.04, The experimental feasibility was investigated for the resonant scattering of monoenergetic neutrinos emitted in the two-body β decay. A simple general formula shows that the resonance cross section can be as large as of the order of 10-17 cm2. The Mössbauer setup using a solid crystal was examined with a focus on the electronic structure of the emitter and the absorber. Based on realistic calculations, we show that interactions of valence electrons in the solid lead to a level broadening of the atomic ground state, which considerably suppresses the resonant scattering of neutrinos..
52. Y. Ichikawa, T. Kubo, N. Aoi, V. Banerjee, A. Chakrabarti, N. Fukuda, H. Iwasaki, S. Kubono, T. Motobayashi, T. Nakabayashi, T. Nakamura, T. Nakao, T. Okumura, H. J. Ong, T. K. Onishi, D. Suzuki, H. Suzuki, M. K. Suzuki, T. Teranishi, K. N. Yamada, H. Yamaguchi, H. Sakurai, Beta-decay study of Tz = - 2 proton-rich nucleus 24Si, European Physical Journal A, 10.1140/epja/i2008-10761-8, 42, 3, 375-378, 2009.12, β-decay spectroscopy on a Tz = - 2 proton-rich nucleus 24Si was performed. The decay scheme of 24Si was reconstructed by the β-delayed γ-ray and proton measurements. Two β branches to the bound 11+ and 12+ states in 24Al were observed for the first time. The observation of the allowed transition firmly established the spin-parity assignment for the 12+ states. The branching ratios to the 11+ and 12+ states were determined to be 31(4)% and 23.9(15)%, respectively. The branching ratios to three unbound states in 24Al including a new level at 6.735MeV were also determined for the first time. The level structure of 24Al was compared with its mirror nucleus 24Na. The Thomas-Ehrman shift on the 12+ state indicates s-wave dominance in the state as well as a characteristic behavior of the weakly bound s-wave proton in 24Al..
53. T. Nagatomo, K. Shimada, K. Asahi, D. L. Balabanski, J. M. Daugas, M. Depuydt, M. de Rydt, L. Gaudefroy, S. Grévy, Y. Hasama, Y. Ichikawa, D. Kameda, P. Morel, L. Perrot, C. Stödel, J. C. Thomas, W. Vanderheijden, N. Vermeulen, P. Vingerhoets, A. Yoshimi, G. Neyens, H. Ueno, Electric quadrupole moment of the neutron-rich 33Al, European Physical Journal A, 10.1140/epja/i2009-10885-3, 42, 3, 383-385, 2009.12, The nuclear electric quadrupole moment (Q moment) of the neutron-rich nucleus 33Al (I = 5/2, T1/2 = 41 ms) has been measured by the β-ray detected nuclear quadrupole resonance (β-NQR) method for the first time. The 33Al nucleus is considered to be on the border of the island of inversion within which a significant intrusion of the pf orbits occurs across the N = 20 shell gap and the intrusion causes an anomalous enhancement of the Q moment. Polarized 33Al nuclei were produced from 36S (77.5 MeV/u) beams through the fragmentation process and separated by LISE fragment separator at GANIL. The 33Al nuclei were implanted into a Al2O3 single-crystal plate and the β-NQR spectrum was successfully obtained..
54. H. J. Ong, N. Imai, D. Suzuki, H. Iwasaki, H. Sakurai, T. K. Onishi, M. K. Suzuki, S. Ota, S. Takeuchi, T. Nakao, Y. Togano, Y. Kondo, N. Aoi, H. Baba, S. Bishop, Y. Ichikawa, M. Ishihara, T. Kubo, K. Kurita, T. Motobayashi, T. Nakamura, T. Okumura, Y. Yanagisawa, Observation/confirmation of hindered E2 strength in 18C/16C, European Physical Journal A, 10.1140/epja/i2009-10804-8, 42, 3, 393-396, 2009.12, We have measured the lifetime of the first excited 2+ state in 18C using an upgraded recoil shadow method to determine the electric quadrupole transition. The measured mean lifetime is 18.9±0.9 (stat)±4.4 (syst) ps, corresponding to, or about 1.5 Weisskopf units. The mean lifetime of the first 2+ state in 16C was remeasured to be 18.3±1.4±4.8 ps, about four times shorter than the value reported previously. The discrepancy is explained by incorporating the γ-ray angular distribution obtained in this work into the previous measurement. The observed transition strengths in 16, 18C are hindered compared to the empirical values, indicating that the anomalous E2 strength observed in 16C persists in 18C..
55. M. Niikura, E. Ideguchi, N. Aoi, H. Baba, T. Fukuchi, Y. Ichikawa, H. Iwasaki, T. Kubo, M. Kurokawa, M. Liu, S. Michimasa, T. Ohnishi, T. K. Onishi, S. Ota, S. Shimoura, H. Suzuki, D. Suzuki, Y. Wakabayashi, K. Yoshida, Y. Zheng, Yrast spectroscopy in 49-51Ti via fusion-evaporation reaction induced by a radioactive beam, European Physical Journal A, 10.1140/epja/i2009-10857-7, 42, 3, 471-475, 2009.12, In-beam γ-ray spectroscopy of high-spin states in 49-51Ti was performed via the fusion-evaporation reaction using a radioactive beam. By excitation function and γ-γ coincidence analysis, yrast high-spin levels up to I = (21/2-),(11+),(17/2-) in 49-51Ti were determined. The levels were compared with full-pf -shell model calculation. The level structure indicates the persistency of the N = 28 shell gap at yrast states in 49-51Ti..
56. Y. Ichikawa, T. K. Onishi, D. Suzuki, H. Iwasaki, V. Banerjee, T. Kubo, A. Chakrabarti, N. Aoi, B. A. Brown, N. Fukuda, S. Kubono, T. Motobayashi, T. Nakabayashi, T. Nakamura, T. Nakao, T. Okumura, H. J. Ong, H. Suzuki, M. K. Suzuki, T. Teranishi, K. N. Yamada, H. Yamaguchi, H. Sakurai, Investigation into behavior of weakly-bound proton via B(GT) measurement for the β decay of 24Si, International Conference on Nuclear Structure and Dynamics '09 Nuclear Structure and Dynamics '09 - Proceedings of the International Conference, 10.1063/1.3232163, 98-101, 2009.11, The β-decay spectroscopy on 24Si was carried out in order to investigate the behavior of a weakly-bound s-wave proton. We observed two β transitions to low-lying bound states in 24Al for the first time. The Gamow-Teller transition strengths B(GT) to the 1+ 1 and 1+2 states were deduced to be 0.13(2) and 0.14(1), which were smaller than that of mirror nucleus 24Ne by 22 % and 10%, respectively. These mirror asymmetries of B(GT) indicate the configuration change in the wave function. By comparing with theoretical shell-model calculations, it is implied that the configuration change is attributed to the lowering of the Is1/2orbital..
57. Y. Ichikawa, T. K. Onishi, D. Suzuki, H. Iwasaki, T. Kubo, V. Naik, A. Chakrabarti, N. Aoi, B. A. Brown, N. Fukuda, S. Kubono, T. Motobayashi, T. Nakabayashi, T. Nakamura, T. Nakao, T. Okumura, H. J. Ong, H. Suzuki, M. K. Suzuki, T. Teranishi, K. N. Yamada, H. Yamaguchi, H. Sakurai, β Decay of the proton-rich nucleus 24Si and its mirror asymmetry, Physical Review C - Nuclear Physics, 10.1103/PhysRevC.80.044302, 80, 4, 2009.10, β-decay spectroscopy of the proton-rich nucleus 24Si was performed. The decay scheme was reconstructed from results of delayed γ-ray and proton measurements. We observed two β branches to bound states in 24Al for the first time. The branching ratios were determined to be 31(4)% and 23.9(15)% for the 11+ state at 0.426 MeV and the state at 1.090 MeV, respectively. The observation of an allowed transition to the 1.090-MeV state enabled us to firmly determine its spin-parity as 1+. In the proton measurements performed with the ΔE-E method, we observed a new unbound level at 6.735 MeV. The branching ratios to three unbound states, including the new level, were also determined for the first time. Based on the decay scheme, the B(GT) values of 24Si were deduced. The B(GT) values were smaller than those of the mirror nucleus 24Ne by 22% and 10% for the 11+ and 12+ states, respectively. The mirror asymmetries of B(GT), observed in both the 11+ and the 12+ states, indicate changes in configuration in the wave function associated with the Thomas-Ehrman shift. To clarify the mechanism of this asymmetry, a comparison with shell-model calculations is also discussed. The calculations attribute the changes in configuration to the lowering of the 1s1/2 orbital..
58. M. De Rydt, G. Neyens, K. Asahi, D. L. Balabanski, J. M. Daugas, M. Depuydt, L. Gaudefroy, S. Grévy, Y. Hasama, Y. Ichikawa, P. Morel, T. Nagatomo, T. Otsuka, L. Perrot, K. Shimada, C. Stödel, J. C. Thomas, H. Ueno, Y. Utsuno, W. Vanderheijden, N. Vermeulen, P. Vingerhoets, A. Yoshimi, Precision measurement of the electric quadrupole moment of 31Al and determination of the effective proton charge in the sd-shell, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2009.06.043, 678, 4, 344-349, 2009.07, The electric quadrupole coupling constant of the 31Al ground state is measured to be νQ = | frac(e Q Vz z, h) | = 2196 (21)   kHz using two different β-NMR (Nuclear Magnetic Resonance) techniques. For the first time, a direct comparison is made between the continuous rf technique and the adiabatic fast passage method. The obtained coupling constants of both methods are in excellent agreement with each other and a precise value for the quadrupole moment of 31Al has been deduced: | Q (31Al) | = 134.0 (16)   mb. Comparison of this value with large-scale shell-model calculations in the sd and sdpf valence spaces suggests that the 31Al ground state is dominated by normal sd-shell configurations with a possible small contribution of intruder states. The obtained value for | Q (31Al) | and a compilation of measured quadrupole moments of odd-Z even-N isotopes in comparison with shell-model calculations shows that the proton effective charge ep = 1.1 e provides a much better description of the nuclear properties in the sd-shell than the adopted value ep = 1.3 e..
59. Hooi Jin Ong, Nobuaki Imai, Daisuke Suzuki, Hironori Iwasaki, Takeo Onishi, Masaru Suzuki, Taro Nakao, Yuichi Ichikawa, Shinsuke Ota, Hiroyoshi Sakurai, Satoshi Takeuchi, Nori Aoi, Hidetada Baba, Shawn Bishop, Masayasu Ishihara, Toshiyuki Kubo, Tohru Motobayashi, Yoshiyuki Yanagisawa, Yasuhiro Togano, Kazuo Kurita, Yosuke Kondo, Takashi Nakamura, Toshifumi Okumura, Anomalously hindered E2 strengths in 16,18C, International Journal of Modern Physics A, 10.1142/S0217751X09045753, 24, 11, 2168-2174, 2009.04, Lifetime measurement of the first excited 2+ state in 18C was performed using an upgraded recoil shadow method to determine the electric quadrupole transition. The measured mean lifetime is 18.9 ± 0.9 (stat) ± 4.4 (syst) ps, which corresponds to a B(E2;2 1+→ 0gs+ value of 4.3 ± 0.2 ± 1.0 e2fm4, or about 1.5 Weisskopf units. The mean lifetime of the first 2+ state in 16C was remeasured to be about 18 ps, about four times shorter than the value reported previously. By incorporating the γ-ray angular distribution measured in this work into the previous measurement, this discrepancy has been explained. The observed transition strengths in 16,18C are hindered compared to the empirical transition strengths, indicating that the anomalous hindered E2 strength observed in 16C persists in 18C..
60. D. Suzuki, H. Iwasaki, H. J. Ong, N. Imai, H. Sakurai, T. Nakao, N. Aoi, H. Baba, S. Bishop, Y. Ichikawa, M. Ishihara, Y. Kondo, T. Kubo, K. Kurita, T. Motobayashi, T. Nakamura, T. Okumura, T. K. Onishi, S. Ota, M. K. Suzuki, S. Takeuchi, Y. Togano, Y. Yanagisawa, Lifetime measurements of excited states in 17C
Possible interplay between collectivity and halo effects, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2008.07.055, 666, 3, 222-227, 2008.08, Lifetime measurements were performed on low-lying excited states of the neutron-rich isotope 17C using the recoil shadow method. The γ-decay mean lifetimes were determined to be 583 ± 21 (stat) ± 35 (syst) ps for the first excited state at 212 keV and 18.9 ± 0.6 (stat) ± 4.7 (syst) ps for the second excited state at 333 keV. Based on a comparison with the empirical upper limits for the electromagnetic transition strengths, these decays are concluded to be predominantly M1 transitions. The reduced M1 transition probabilities to the ground state were deduced to be (1.0 ± 0.1) × 10-2 μN2 and (8.2-1.8+3.2) × 10-2 μN2, respectively, for the first and second excited states. The strongly hindered M1 strength as well as the lowered excitation energy represents unique nature of the 212-keV state..
61. H. Iwasaki, S. Michimasa, M. Niikura, M. Tamaki, N. Aoi, H. Sakurai, S. Shimoura, S. Takeuchi, S. Ota, M. Honma, T. K. Onishi, E. Takeshita, H. J. Ong, H. Baba, Z. Elekes, T. Fukuchi, Y. Ichikawa, M. Ishihara, N. Iwasa, S. Kanno, R. Kanungo, S. Kawai, T. Kubo, K. Kurita, T. Motobayashi, A. Saito, Y. Satou, H. Suzuki, M. K. Suzuki, Y. Togano, Y. Yanagisawa, Persistence of the N=50 shell closure in the neutron-rich isotope Ge80, Physical Review C - Nuclear Physics, 10.1103/PhysRevC.78.021304, 78, 2, 2008.08, The 21+ and 22+ states of the neutron-rich isotope Ge80 were studied by intermediate-energy heavy-ion scattering, providing for the first time the experimental value of B(E2;22+→0g.s.+) for Ge80. The experimental data are well reproduced by large-scale shell model calculations, which suggest the important role of the proton particle-hole 2p3/2-1f5/2 excitation in the configuration of the 22+ state..
62. H. J. Ong, N. Imai, D. Suzuki, H. Iwasaki, H. Sakurai, T. K. Onishi, M. K. Suzuki, S. Ota, S. Takeuchi, T. Nakao, Y. Togano, Y. Kondo, N. Aoi, H. Baba, S. Bishop, Y. Ichikawa, M. Ishihara, T. Kubo, K. Kurita, T. Motobayashi, T. Nakamura, T. Okumura, Y. Yanagisawa, Lifetime measurements of first excited states in C16,18, Physical Review C - Nuclear Physics, 10.1103/PhysRevC.78.014308, 78, 1, 2008.07, The electric quadrupole transition from the first 2+ state to the ground 0+ state in C18 was studied through a lifetime measurement by an upgraded recoil shadow method applied to inelastically scattered radioactive C18 nuclei. The measured mean lifetime is 18.9±0.9(stat)±4.4(syst) ps, corresponding to a B(E2;21+→0g.s.+) value of 4.3±0.2±1.0e2 fm4, or about 1.5 Weisskopf units. The mean lifetime of the first 2+ state in C16 was remeasured to be 18.3±1.4±4.8 ps, about four times shorter than the value reported previously. The discrepancy between the two results was explained by incorporating the γ-ray angular distribution measured in this work into the previous measurement. These transition strengths are hindered compared to the empirical transition strengths, indicating that the anomalous hindrance observed in C16 persists in C18..
63. S. Sakaguchi, T. Uesaka, T. Wakui, T. Kawabata, N. Aoi, Y. Hashimoto, M. Ichikawa, Y. Ichikawa, K. Itoh, M. Itoh, H. Iwasaki, T. Kawahara, H. Kuboki, Y. Maeda, R. Matsuo, T. Nakao, H. Okamura, H. Sakai, N. Sakamoto, Y. Sasamoto, M. Sasano, Y. Satou, K. Sekiguchi, M. Shinohara, K. Suda, D. Suzuki, Y. Takahashi, A. Tamii, K. Yako, M. Yamaguchi, Analyzing power measurement for elastic scattering of 6He on polarized protons, 17th International Spin Physics Symposium Proceedings of the 17th International Spin Physics Symposium, 10.1063/1.2750906, 833-836, 2007.09, Vector analyzing power was measured for the proton elastic scattering on 6He at 71 MeV/u. We applied a solid polarized proton target, which was operated in a low magnetic field of 88 mT and at high temperature of 100 K, to a radioactive-isotope beam experiment. Low energy recoil protons were successfully detected due to the modest operation conditions of the target. Selection of p+6He elastic scattering events was clearly carried out with detected protons. Absolute values of the analyzing power were determined for the first time..
64. S. Bishop, T. Motobayashi, N. Aoi, T. Gomi, S. Nishimura, T. Ohnishi, A. Perera, T. Sumikama, S. Takeuchi, K. Tanaka, Y. Yanagisawa, Y. Ichikawa, N. Imai, H. Iwasaki, N. Nakao, T. K. Ohnishi, H. J. Ong, D. Suzuki, H. Suzuki, M. K. Suzuki, N. Iwasa, S. Kawai, Y. Togano, Y. Kondo, T. Nakamura, S. Ota, S. Shimoura, M. Tamaki, Elastic scattering of 8B on Pb, liquid hydrogen and liquid helium targets and the 7Be(p,γ)8B S-Factor, 9th International Symposium on Nuclear Astrophysics - Nuclei in the Cosmos, NIC 2006 Proceedings of Science, 2006.12, The solar 7Be(p,γ)8B reaction, occurring in the solar PPIII chain, is responsible for the high energy neutrino flux observed in such facilities as SNO and Super Kamiokande. This neutrino flux is sensitive to the astrophysical S-factor of this reaction, S17. We have performed a 8B Coulomb Dissociation (CD) experiment using Pb, liquid He, and liquid H2 targets in an effort to extract S17. Elastic scattering data of 8B on these 3 targets will be presented along a discussion of their use in analyzing CD data..
65. T. K. Onishi, A. Gelberg, H. Sakurai, K. Yoneda, N. Aoi, N. Imai, H. Baba, P. Von Brentano, N. Fukuda, Y. Ichikawa, M. Ishihara, H. Iwasaki, D. Kameda, T. Kishida, A. F. Lisetskiy, H. J. Ong, M. Osada, T. Otsuka, M. K. Suzuki, K. Ue, Y. Utsuno, H. Watanabe, Beta decay of 46Cr, Journal of Physics: Conference Series, 10.1088/1742-6596/49/1/012, 49, 1, 51-52, 2006.10, The Gamow-Teller transition of 46Cr to the N Z odd-odd nucleus 46V has been observed for the first time. By means of β-γ coincidence measurements, a γ-ray peak at 993 keV corresponding to the decay of the 1+1 state in 46V was observed. The branching ratio of the decay to this state was found to be bGT 0.25 0.050. The half-life of 46Cr was measured to be T1/2 240 140 ms. The transition strength was determined to be B(GT) 0.64 0.20. This result was compared with theoretical calculations..
66. H. Iwasaki, M. Tamaki, S. Michimasa, M. Niikura, S. Shimoura, N. Aoi, S. Takeuchi, S. Ota, T. K. Onishi, E. Takeshita, H. J. Ong, H. Baba, Z. Elekes, T. Fukuchi, Y. Ichikawa, M. Ishihara, N. Iwasa, S. Kanno, R. Kanungo, S. Kawai, T. Kubo, K. Kurita, A. Saito, Y. Satou, H. Suzuki, M. K. Suzuki, Y. Togano, Y. Yanagisawa, H. Sakurai, T. Motobayashi, Spectroscopy on neutron-rich nuclei near N =50 via two-step Coulomb excitation at intermediate energies, Journal of Physics: Conference Series, 10.1088/1742-6596/49/1/015, 49, 1, 65-66, 2006.10, We have investigated structure of the neutron-rich Ge isotopes at and around N 50 via intermediate-energy Coulomb excitation. A new method of intermediate-energy twostep Coulomb excitation has been tested to study the second excited states, such as the 2+2 and 4 +1states, in neutron-rich even-even nuclei. The first application of the method and its results are presented..
67. M. Hatano, H. Sakai, T. Wakui, T. Uesaka, N. Aoi, Y. Ichikawa, T. Ikeda, K. Itoh, H. Iwasaki, T. Kawabata, H. Kuboki, Y. Maeda, N. Matsui, T. Ohnishi, T. K. Onishi, T. Saito, N. Sakamoto, M. Sasano, Y. Satou, K. Sekiguchi, K. Suda, A. Tamii, Y. Yanagisawa, K. Yako, First experiment of 6He with a polarized proton target, European Physical Journal A, 10.1140/epjad/i2005-06-110-5, 25, SUPPL. 1, 255-258, 2005.09, We have constructed a new type of spin polarized solid proton target which can be operated under a low magnetic field of 0.08T and a high temperature of 100K. We have measured for the first time the polarization asymmetry of an unstable beam of 6He at an energy of 71MeV/u. Optical potential analyses have been carried out..
68. H. Iwasaki, N. Aoi, S. Takeuchi, S. Ota, H. Sakurai, M. Tamaki, T. K. Onishi, E. Takeshita, H. J. Ong, N. Iwasa, H. Baba, Z. Elekes, T. Fukuchi, Y. Ichikawa, M. Ishihara, S. Kanno, R. Kanungo, S. Kawai, T. Kubo, K. Kurita, S. Michimasa, M. Niikura, A. Saito, Y. Satou, S. Shimoura, H. Suzuki, M. K. Suzuki, Y. Togano, Y. Yanagisawa, T. Motobayashi, Intermediate-energy Coulomb excitation of the neutron-rich Ge isotopes around N = 50, European Physical Journal A, 10.1140/epjad/i2005-06-154-5, 25, SUPPL. 1, 415-417, 2005.09, Structure of the neutron-rich Ge isotopes at and around N = 50 has been investigated via intermediate-energy Coulomb excitation using secondary beams of 78-82Ge incident on a Pb target. The B(E2) values for the low-lying 2+ states have been extracted and compared with the data for neighboring isotopes around N = 50. In addition, a new method of intermediate-energy two-step Coulomb excitation has been proposed as a spectroscopic tool to study the 4+ states in neutron-rich even-even nuclei. The first application of the method and its results are presented..
69. Zs Dombrádi, Z. Elekes, R. Kanungo, H. Baba, Zs Fülöp, J. Gibelin, Á Horváth, E. Ideguchi, Y. Ichikawa, N. Iwasa, H. Iwasaki, S. Kanno, S. Kawai, Y. Kondo, T. Motobayashi, M. Notani, T. Ohnishi, A. Ozawa, H. Sakurai, S. Shimoura, E. Takeshita, S. Takeuchi, I. Tanihata, Y. Togano, C. Wu, Y. Yamaguchi, Y. Yanagisawa, A. Yoshida, K. Yoshida, Decoupling of valence neutrons from the core in 17B, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2005.06.031, 621, 1-2, 81-88, 2005.08, Proton inelastic scattering study of 17B nucleus has been performed at 43.8 A MeV average energy in inverse kinematics using a liquid hydrogen target. In the Doppler corrected γ ray spectrum, a single peak with an energy of 1089(15) keV appeared corresponding to the first excited state of 17B. Based on the reaction cross section, β2pp′ deformation parameter of the transition is deduced by distorted wave analysis. Comparing it with the electric quadrupole moment of the nucleus, it is shown that the deformation of the neutron distribution is large (βn∼0.6), and the neutron effective charge is much smaller (en<0.12) than usual (∼0.5). The small effective charge is interpreted as a consequence of the decoupling of valence neutrons from the core..
70. T. K. Onishi, A. Gelberg, H. Sakurai, K. Yoneda, N. Aoi, N. Imai, H. Baba, P. Von Brentano, N. Fukuda, Y. Ichikawa, M. Ishihara, H. Iwasaki, D. Kameda, T. Kishida, A. F. Lisetskiy, H. J. Ong, M. Osada, T. Otsuka, M. K. Suzuki, K. Ue, Y. Utsuno, H. Watanabe, Gamow-teller decay of the T=1 nucleus Cr46, Physical Review C - Nuclear Physics, 10.1103/PhysRevC.72.024308, 72, 2, 2005.08, The Gamow-Teller β decay of Cr46 to the N=Z odd-odd nucleus V46 has been observed for the first time. Cr46 was produced by the fragmentation of a Cr50 primary beam at 80 MeV/nucleon. By means of β-γ coincidence measurements, a γ-ray peak at 993 keV corresponding to the decay of the 11+ state in V46 was observed. The branching ratio of the Gamow-Teller decay to this state was found to be bGT=0.216±0.050. The half-life of Cr46 was measured to be T1/2=240±140 ms. The transition strength was determined to be B(GT)=0.64±0.20. This result was compared with theoretical values calculated with the shell model and the phenomenological quasideuteron model..
71. Ritu Kanungo, Z. Elekes, H. Baba, Zs Dombrádi, Zs Fülöp, J. Gibelin, Á Horváth, Y. Ichikawa, E. Ideguchi, N. Iwasa, H. Iwasaki, S. Kawai, Y. Kondo, T. Motobayashi, M. Notani, T. Ohnishi, A. Ozawa, H. Sakurai, S. Shimoura, E. Takeshita, S. Takeuchi, I. Tanihata, Y. Togano, C. Wu, Y. Yamaguchi, Y. Yanagisawa, A. Yoshida, K. Yoshida, Search for an isomeric state in 19C, Nuclear Physics A, 10.1016/j.nuclphysa.2005.04.015, 757, 3-4, 315-328, 2005.08, A search for an isomeric state in the neutron-rich nucleus 19C is reported. The existence of an isomer in the nucleus is predicted by shell model calculations which also predicts the ground-state of the nucleus to be 1/2+. An isomeric transition is however not observed in the present investigation. An estimation of upper limit of isomer ratio in the beam is discussed. Furthermore, the non-observation of an isomer includes the possibility of 19C having a different ground state spin. The 17C and 17B nuclei were also investigated for delayed gamma transitions but do not exhibit any isomeric transition..
72. Z. Elekes, Zs Dombrádi, R. Kanungo, H. Baba, Zs Fülöp, J. Gibelin, Á Horváth, E. Ideguchi, Y. Ichikawa, N. Iwasa, H. Iwasaki, S. Kanno, S. Kawai, Y. Kondo, T. Motobayashi, M. Notani, T. Ohnishi, A. Ozawa, H. Sakurai, S. Shimoura, E. Takeshita, S. Takeuchi, I. Tanihata, Y. Togano, C. Wu, Y. Yamaguchi, Y. Yanagisawa, A. Yoshida, K. Yoshida, Low-lying excited states in 17,19C, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2005.04.007, 614, 3-4, 174-180, 2005.05, 17,19C nuclei have been investigated by proton inelastic scattering on a liquid hydrogen target at intermediate energies. Two peaks were observed in the Doppler-corrected γ-ray spectra with energies of 210(6), 331(6) keV in 17C and 72(4), 197(6) keV in 19C corresponding to the decay of two excited states in both nuclei. Analyzing the reaction cross sections, tentative spin values were determined for the states. The experimental results are in reasonable agreement with the predictions by shell model calculations..
73. M. Hatano, H. Sakai, T. Wakui, T. Uesaka, N. Aoi, Y. Ichikawa, T. Ikeda, K. Itoh, H. Iwasaki, T. Kawabata, H. Kuboki, Y. Maeda, N. Matsui, T. Ohnishi, T. K. Onishi, T. Saito, N. Sakamoto, M. Sasano, Y. Satou, K. Sekiguchi, K. Suda, A. Tamii, Y. Yanagisawa, K. Yako, 6He scattering with polarized proton target, Nuclei at the Limits NUCLEI AT THE LIMITS, 10.1063/1.1905336, 360-364, 2005.04, A new type of the spin polarized solid proton target has been constructed which can be operated under a low magnetic field of 0.08 T and a high temperature of 100 K. First polarization asymmetry measurement with an unstable beam of 6He with an energy of 71 MeV/u has been successfully carried out..
74. R. Kanungo, Z. Elekes, H. Baba, Zs Dombrádi, Zs Fülöp, J. Gibelin, Á Horváth, Y. Ichikawa, E. Ideguchi, N. Iwasa, H. Iwasaki, S. Kawai, Y. Kondo, T. Motobayashi, M. Notani, T. Ohnishi, A. Ozawa, H. Sakurai, S. Shimoura, E. Takeshita, S. Takeuchi, I. Tanihata, Y. Togano, C. Wu, Y. Yamaguchi, Y. Yanagisawa, A. Yoshida, K. Yoshida, Excited states in neutron rich boron isotopes, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2005.01.022, 608, 3-4, 206-214, 2005.02, New experimental results on in-beam gamma spectroscopy of neutron rich boron isotopes are presented for 17B and its neutron removal fragments 14,15B, after scattering with a H2 target. A gamma transition for 17B is observed at 1089±15 keV. The fragment 15B is observed abundantly associated with a gamma transition of 1336±10 keV. This suggests for the first time a core-excited structure for 17B thereby providing a new insight into its structure. Observations for 12,14B are also presented. The data set provides a useful systematic study of first excited states of neutron rich boron isotopes showing the dramatic drop in excitation energy beyond N = 8..