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Journal Articles

Nature of isomerism in exotic sulfur isotopes

Utsuno, Yutaka; Shimizu, Noritaka*; Otsuka, Takaharu*; Yoshida, Toru*; Tsunoda, Yusuke*

Physical Review Letters, 114(3), p.032501_1 - 032501_5, 2015/01

AA2014-0621.pdf:0.23MB

https://doi.org/10.1103/PhysRevLett.114.032501
 Times Cited Count：37 Percentile：85.46(Physics, Multidisciplinary)

In usual even-even nuclei, $$0^+_1$$, $$2^+_1$$, $$4^+_1cdots$$ states are known to be connected via strong $$E2$$ transitions. The recently observed $$4^+_1$$ state in the neutron-rich nucleus $$^{44}$$S has a strongly hindered $$E2$$ transition to the $$4^+_1$$ state. We report the origin of this strong hindrance in this paper. While shell-model calculations reproduce the hindrance, their many-body wave functions are too complicated for one to understand the nature. In this study, we introduce a novel method to obtain wave functions in the intrinsic frame by performing the variation after angular-momentum projection. The $$0^+_1$$, $$2^+_1$$ states are dominated by the usual $$K=0$$ state, whereas for the $$4+$$ level the $$K=4$$ state is lower than $$K=0$$ state, which causes the $$E2$$ hindrance. We also account for similar $$E2$$ hindrance in $$^{43}$$S in this framework. The $$4^+$$ level is the lightest-mass high-$$K$$ isomer ever found.

Journal Articles

Identification of the $$K^pi=11/2^+$$ isomer in neutron-rich $$^{187}$$W

Shizuma, Toshiyuki; Hayakawa, Takehito; Mitarai, Shiro*; Morikawa, Tsuneyasu*; Ishii, Tetsuro

Physical Review C, 71(6), p.067301_1 - 067301_4, 2005/06

https://doi.org/10.1103/PhysRevC.71.067301
 Times Cited Count：6 Percentile：45.53(Physics, Nuclear)

Excited states in neutron-rich $$^{187}$$W have been populated via deep inelastic collisions of a 630-MeV $$^{82}$$Se beam on a $$^{186}$$W target. Projectile-like fragments were measured by an annular Si detector for reaction channel selection. Delayed $$gamma$$ rays from target residues were detected by means of the so-called recoil shadow technique. A new isomer at 411 keV, based on the $$11/2^+$$[615] Nilsson configuration, has been identified with the half-life of 1.56(28) $$mu$$s. The decay rates of the isomers are discussed in terms of the $$K$$ quantum number by comparison with the systematics from the neighboring nuclei.

Journal Articles

A New isomer in $$^{136}$$Ba populated by deep inelastic collisions

Shizuma, Toshiyuki; Gan, Z. G.*; Ogawa, Kengo*; Nakada, Hitoshi*; Oshima, Masumi; Toh, Yosuke; Hayakawa, Takehito; Hatsukawa, Yuichi; Sugawara, Masahiko*; Utsuno, Yutaka; et al.

European Physical Journal A, 20(2), p.207 - 210, 2004/04

https://doi.org/10.1140/epja/i2003-10163-6
 Times Cited Count：13 Percentile：71.74(Physics, Nuclear)

Excited states in $$^{136}$$Ba, populated in deep-inelastic collisions by the interaction of 450-MeV $$^{82}$$Se ions with a $$^{139}$$La target, have been studied by means of in-beam $$gamma$$-ray spectroscopy. A new isomer with $$I^pi=(10^+)$$ has been identified at an excitation energy of $$E_x=3.357$$ MeV. The half-life was determined as $$T_{1/2}=94pm10$$ ns. The extracted $$B(E2)$$ value is much smaller than those in $$^{132}$$Te and $$^{134}$$Xe. This hindrance is investigated by a shell model calculation.

Journal Articles

High-spin structure in $$^{185}$$Os

Shizuma, Toshiyuki; Mitarai, Shiro*; Sletten, G.*; Bark, R. A.*; Gjorup, N. L.*; Jensen, H. J.*; Piiparinen, M.*; Wrzesinski, J.*; Shimizu, Yoshifumi*

Physical Review C, 69(2), p.024305_1 - 024305_18, 2004/02

https://doi.org/10.1103/PhysRevC.69.024305
 Times Cited Count：15 Percentile：65.31(Physics, Nuclear)

High-spin states in $$^{185}$$Os have been studied using the $$^{176}$$Yb($$^{13}$$C,4n) reaction at a beam energy of 65MeV. Previously known 1-quasiparticle bands have been extended to higher spins. New high-$$K$$ bands based on 3- and 5-quasiparticle excitation have been identified. Nilsson configurations are assigned based on the g-factors deduced from M1/E2 branching ratios within the bands. In addition, a new isomer at 5008keV has been found with a half-life of 18(2) ns. The hindrance in decays of the high-$$K$$ intrinsic states are discussed in terms of the $$gamma$$ tunneling model where the low-$$K$$ and high-$$K$$ states interact through the triaxial shape fluctuation.

Journal Articles

Inelastic excitation of $$^{187}$$Re

Shizuma, Toshiyuki; Toh, Yosuke; Oshima, Masumi; Sugawara, Masahiko*; Matsuda, Makoto; Hayakawa, Takehito; Koizumi, Mitsuo; Osa, Akihiko; Zhang, Y. H.*; Liu, Z.*

European Physical Journal A, 17(2), p.159 - 165, 2003/06

https://doi.org/10.1140/epja/i2002-10156-y
 Times Cited Count：10 Percentile：55.62(Physics, Nuclear)

High-spin states in $$^{187}$$Re populated by inelastic scattering of a 500-MeV $$^{82}$$Se beam have been studied by means of in-beam $$gamma$$-ray spectroscopy. Levels built on the $$5/2^+$$[402] and $$9/2^-$$[514] one-quasiparticle states were measured up to $$I^pi=(21/2^+)$$ and $$(21/2^-)$$, respectively. In additions, several new levels including an isomer at 1682 keV with a half-life of 114(23) ns have been found. Quasiparticle configurations of the levels and the transition rates are discussed.

Journal Articles

Neutron capture cross section to $$^{186}$$Re isomeric state

Hayakawa, Takehito; Shizuma, Toshiyuki; Yamauchi, Toshihiko; Minehara, Eisuke; Arisawa, Takashi

Nuclear Physics A, 718, p.665c - 667c, 2003/05

no abstracts in English

Journal Articles

Tunneling in high-$$K$$ isomeric decays

Shizuma, Toshiyuki; Shimizu, Yoshifumi*; Hayakawa, Takehito

Journal of Nuclear Science and Technology, 39(11), p.1137 - 1141, 2002/11

https://doi.org/10.3327/jnst.39.1137
 Times Cited Count：4 Percentile：29.25(Nuclear Science & Technology)

We have systematically investigated the highly $$K$$-forbidden transitions observed in the Hf, W and Os region, using the $$gamma$$-tunneling model in which low-$$K$$ and high-$$K$$ states interact through a process of the quantum tunneling. In the present study, we have analyzed $$K$$-forbidden transitions recently observed. The measured hindrance factors are compared with the values calculated using the $$gamma$$-tunneling model. We have also investigated isotope dependences of $$gamma$$ tunneling probabilities particularly for neutron-rich nuclei.

Journal Articles

High-$$K$$ negative parity states in $$^{184}$$Os

Shizuma, Toshiyuki; Stevenson, P. D.*; Walker, P. M.*; Toh, Yosuke; Hayakawa, Takehito; Oshima, Masumi; Furuno, Kohei*; Komatsubara, Tetsuro*

Physical Review C, 65(6), p.064310_1 - 064310_12, 2002/06

https://doi.org/10.1103/PhysRevC.65.064310
 Times Cited Count：15 Percentile：62.9(Physics, Nuclear)

High-spin states in $$^{184}$$Os have been studied using the $$^{170}$$Er($$^{18}$$O,4n) reaction at a beam energy of 85 MeV. Several new negative parity levels including a 48-ns $$K^pi=(18^-)$$ isomer have been identified. Nilsson configurations for the levels are assigned by comparison with multi-quasiparticle calculations. Potential-energy-surface calculations show an increasing influence of triaxiality in nuclear shapes at higher spins. The decay rate of the $$K^pi=(18^-)$$ isomer is discussed in relation to the role of the $$K$$ quantum number.

Journal Articles

Multi-quasiparticle states and ${it K}$-forbidden transitions in $$^{183}$$Os

Shizuma, Toshiyuki; Matsuura, Katsuyuki*; Toh, Yosuke; Hayakawa, Takehito; Oshima, Masumi; Hatsukawa, Yuichi; Matsuda, Makoto; Furuno, Kohei*; Sasaki, Yasuyuki*; Komatsubara, Tetsuro*; et al.

Nuclear Physics A, 696(3-4), p.337 - 370, 2001/12

https://doi.org/10.1016/S0375-9474(01)01210-6
 Times Cited Count：20 Percentile：73.84(Physics, Nuclear)

High-spin states in $$^{183}$$Os have been studied using the 170Er(18O,5n) reaction at a beam energy of 85 MeV. Nine rotational bands based on 1-, 3-, 5- and 7-quasiparticle excitations have been observed. Nilsson configurations are assigned for the newly observed bands using g-factors deduced from M1/E2 branching ratios within the bands. In addition, two isomers with K=(43/2+) and (43/2-) have been identified. The K=(43/2+) isomer decays directly to the K=9/2+ ground state band with a large difference in the $$K$$ quantum number, $$mitDelta K=$$17. The decay rates are disccused in terms of a tunneling model where high-$$K$$ (isomeric) and low-$$K$$ states interact via fluctuations towards triaxial nuclear shapes.

Journal Articles

Present status of advanced photon science research program related to X-, and $$gamma$$-ray emission source development

Arisawa, Takashi; Matoba, Toru; Yamakawa, Koichi; Maruyama, Yoichiro; Sasuga, Tsuneo; Wakaida, Ikuo; Nakajima, Kazuhisa*; Sasaki, Akira; Minehara, Eisuke; Oshima, Masumi

Proc. of the 1st International Induced Gamma Emision Workshop, p.29 - 41, 1999/00

no abstracts in English

Journal Articles

Coulomb excitation of $$^{174}$$Hf K-isomer; $$gamma$$-ray spectroscopy with high-spin isomer beam

Morikawa, Tsuneyasu*; *; Morita, Kosuke*; *; Murakami, Takeshi*; *; *; G.H.Liu*; A.Ferragut*; *; et al.

Physics Letters B, 350, p.169 - 172, 1995/00

https://doi.org/10.1016/0370-2693(95)00345-L
 Times Cited Count：19 Percentile：71.02(Astronomy & Astrophysics)

no abstracts in English

Journal Articles

Isomeric Yield ratio for the $$^{95}$$Mo(p,n) $$^{95m,g}$$Tc reaction

Nagame, Yuichiro; *; *

Applied Radiation and Isotopes, 45(3), p.281 - 285, 1994/00

https://doi.org/10.1016/0969-8043(94)90040-X
 Times Cited Count：5 Percentile：47.66(Chemistry, Inorganic & Nuclear)

no abstracts in English

JAEA Reports

Activation cross section data file, II

*; Iijima, Shungo*; Asami, Tetsuo*

JAERI-M 91-006, 65 Pages, 1991/02

JAERI-M-91-006.pdf:1.41MB

no abstracts in English

Journal Articles

Isomeric yield ratios in proton, $$^{3}$$He-, and $$alpha$$-particle-induced reactions on $$^{197}$$Au

Nagame, Yuichiro; Sueki, Keisuke*; *; Nakahara, Hiromichi*

Physical Review C, 41(3), p.889 - 897, 1990/03

https://doi.org/10.1103/PhysRevC.41.889
 Times Cited Count：32 Percentile：84.91(Physics, Nuclear)

no abstracts in English

Oral presentation

Discovery of $$^{234m}$$Np isomer

Kamada, Hiroki*; Asai, Masato; Tsukada, Kazuaki; Sato, Tetsuya; Toyoshima, Atsushi; Nagame, Yuichiro; Mitsukai, Akina; Tomitsuka, Tomohiro*; Andreyev, A. N.; Nishio, Katsuhisa; et al.

no journal, , 

Existence of the previously unknown isomer $$^{234m}$$Np was discovered for the first time. $$^{234m}$$Np was produced by using the JAEA tandem accelerator. Short-lived reaction products were mass-separated by the on-line isotope separator ISOL, and $$gamma$$ and X rays originating from the decay of $$^{234m}$$Np were observed. The half-life of $$^{234m}$$Np was determined to be approximately 9 min, and $$^{234m}$$Np was found to decay via the EC decay as well as the isomeric transition. On the basis of the observed $$gamma$$ and X rays and the half-life value, we have evaluated level energy, spin-parity, and proton-neutron configuration of $$^{234m}$$Np.

Oral presentation

Isomer spectroscopy using actinide targets

Sugiyama, Koichi*; Go, Shintaro*; Tomimatsu, Taro*; Kai, Tamito*; Nagae, Daisuke*; Ishibashi, Yuichi*; Matsunaga, Sotaro*; Nagata, Yuto*; Nishibata, Hiroki*; Washiyama, Kohei*; et al.

no journal, , 

We have successfully performed in-beam gamma-ray spectroscopy using the isomer-scope technique to study excited-state structure of neutron-rich heavy-actinide nuclei. The neutron-rich heavy-actinide nuclei were produced in the multinucleon-transfer reactions with a $$^{248}$$Cm target and $$^{18}$$O projectiles accelerated with the JAEA tandem accelerator. Projectile-like scattered particles were detected with Si E-$$Delta$$E telescopes placed at the backward angle, and target-like scattered particles of isomers were caught by an annular aluminum plate placed at about 60-mm downstream from the target. Four Ge detectors and 4 LaBr detectors were placed at the periphery of the aluminum plate, and detected gamma rays from the isomers. Gamma rays emitted from the actinide isomers were successfully observed with a good sensitivity owing to the tungsten shield placed between the target and the detectors.

16 (Records 1-16 displayed on this page)
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