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論文

The $$^{59}$$Fe(n,$$gamma$$)$$^{60}$$Fe cross section from the surrogate ratio method and its effect on the $$^{60}$$Fe nucleosynthesis

Yan, S. Q.*; Li, X. Y.*; 西尾 勝久; Lugaro, M.*; Li, Z. H.*; 牧井 宏之; Pignatari, M.*; Wang, Y. B.*; Orlandi, R.; 廣瀬 健太郎; et al.

Astrophysical Journal, 919(2), p.84_1 - 84_7, 2021/10

 被引用回数:1 パーセンタイル:9.31(Astronomy & Astrophysics)

The long-lived $$^{60}$$Fe (with a half-life of 2.62 Myr) is a crucial diagnostic of active nucleosynthesis in the Milky Way galaxy and in supernovae near the solar system. The neutron-capture reaction $$^{59}$$Fe(n,$$gamma$$)$$^{60}$$Fe on $$^{59}$$Fe (half-life=44.5 days) is the key reaction for the production of $$^{60}$$Fe in massive stars. This reaction cross section has been previously constrained by the Coulomb dissociation experiment, which offered partial constraint on the E1 $$gamma$$-ray strength function but a negligible constraint on the M1 and E2 components. In this work, for the first time, we use the surrogate ratio method to experimentally determine the $$^{59}$$Fe(n,$$gamma$$)$$^{60}$$Fe cross sections in which all the components are included. We derived a Maxwellian-averaged cross section of 27.5$$pm$$3.5 mb at $$kT$$ = 30 keV and 13.4$$pm$$1.7 mb at $$kT$$ = 90 keV, roughly 10%-20% higher than previous estimates. We analyzed the impact of our new reaction rates in nucleosynthesis models of massive stars and found that uncertainties in the production of $$^{60}$$Fe from the $$^{59}$$Fe(n,$$gamma$$)$$^{60}$$Fe rate are at most 25$$%$$. We conclude that stellar physics uncertainties now play a major role in the accurate evaluation of the stellar production of $$^{60}$$Fe.

論文

Shell structure of the neutron-rich isotopes $$^{69,71,73}$$Co

Lokotko, T.*; Leblond, S.*; Lee, J.*; Doornenbal, P.*; Obertelli, A.*; Poves, A.*; Nowacki, F.*; 緒方 一介*; 吉田 数貴; Authelet, G.*; et al.

Physical Review C, 101(3), p.034314_1 - 034314_7, 2020/03

 被引用回数:8 パーセンタイル:70.75(Physics, Nuclear)

中性子過剰核である$$^{69,71,73}$$Coに対する($$p,2p$$)ノックアウト反応が理化学研究所RIBFで測定された。$$gamma-gamma$$ coincidenceの方法で準位構造が決定され、測定された包括的断面積および排他的断面積から暫定的ではあるがスピン・パリティが決定された。殻模型計算との比較により、$$^{69,71,73}$$Coの低励起状態には球形核と変形核が共存することが示唆された。

論文

Nuclear structure of $$^{76}$$Ni from the ($$p$$,$$2p$$) reaction

Elekes, Z.*; Kripk$'o$, $'A$*; Sohler, D.*; Sieja, K.*; 緒方 一介*; 吉田 数貴; Doornenbal, P.*; Obertelli, A.*; Authelet, G.*; 馬場 秀忠*; et al.

Physical Review C, 99(1), p.014312_1 - 014312_7, 2019/01

 被引用回数:8 パーセンタイル:64.83(Physics, Nuclear)

($$p$$,$$2p$$)反応による$$^{76}$$Niの核構造の探索実験を行った。Lenzi, Nowacki, Poves, Sieja相互作用を用いた殻模型計算では実験結果を説明しうる陽子空孔状態が得られており、理論的な断面積計算は実験値とよい一致を与えた。実験で得られたすべての状態を理論的に一意に決定することはできなかったが、過去の実験結果と同様にNi同位体でのZ = 28の大きなshell gapを示す結果が得られた。

論文

Shell evolution beyond $$Z$$=28 and $$N$$=50; Spectroscopy of $$^{81,82,83,84}$$Zn

Shand, C. M.*; Podoly$'a$k, Zs.*; G$'o$rska, M.*; Doornenbal, P.*; Obertelli, A.*; Nowacki, F.*; Otsuka, T.*; Sieja, K.*; Tostevin, J. A.*; Tsunoda, T.*; et al.

Physics Letters B, 773, p.492 - 497, 2017/10

 被引用回数:23 パーセンタイル:87.56(Astronomy & Astrophysics)

Low-lying states in neutron-rich $$^{81,82.83.84}$$Zn nuclei were measured for the first time via in-beam $$gamma$$-ray spectroscopy at RIKEN. These include the 4$$_1^+$$ to 2$$_1^+$$ in $$^{82}$$Zn and the 2$$_1^+$$ to 0$$_1^+$$ and 4$$_1^+$$ to 2$$_1^+$$ in $$^{84}$$Zn. The reduced E($$2^+$$) energies and increased E(4$$^+$$)/E(2$$^+$$) ratios at $$N$$=52,54 compared to $$^{80}$$Zn attest that the magicity is confined just on the neutron number $$N$$=50 only. The levels observed in $$^{84}$$Zn suggest the onset of deformation towards heavier Zn isotopes. The data were compared to state-of-the-art shell model calculations.

論文

Shape evolution in neutron-rich krypton isotopes beyond N=60; First spectroscopy of $$^{98,100}$$Kr

Flavigny, F.*; Doornenbal, P.*; Obertelli, A.*; Delaroche, J.-P.*; Girod, M.*; Libert, J.*; Rodriguez, T. R.*; Authelet, G.*; 馬場 秀忠*; Calvet, D.*; et al.

Physical Review Letters, 118(24), p.242501_1 - 242501_6, 2017/06

 被引用回数:34 パーセンタイル:86.96(Physics, Multidisciplinary)

The first $$gamma$$-ray spectroscopy of very neutron rich $$^{98,100}$$Kr isotopes was carried out at the RIBF at RIKEN Nishina center. Excited states in these isotopes were populated via (p,2p) reactions using radioactive $$^{99,101}$$Rb beams accelerated to 220 MeV/nucleon. The new data show a significant increase in deformation beyond N=60, as well as competing configurations (shape-coexistence) at low energy. The data were compared with beyond-mean-field calculations which predict level energies in good agreement with observation, and suggest oblate-prolate shape coexistence.

論文

Low-lying structure and shape evolution in neutron-rich Se isotopes

Chen, S.*; Doornenbal, P.*; Obertelli, A.*; Rodriguez, T. R.*; Authelet, G.*; 馬場 秀忠*; Calvet, D.*; Ch$^a$teau, F.*; Corsi, A.*; Delbart, A.*; et al.

Physical Review C, 95(4), p.041302_1 - 041302_6, 2017/04

 被引用回数:23 パーセンタイル:87.56(Physics, Nuclear)

Neutron-rich isotopes of selenium, $$^{88,90,92,94}$$Se, where studied via in beam $$gamma$$-ray spectroscopy after nucleon removal reactions at RIBF in RIKEN. The low-energy excitations of these nuclei were investigated using $$gamma$$-$$gamma$$ coincidences, and the first and second excited 2$$^+$$ states were found at remarkably low energies. The analysis and comparison with self-consistent beyond-mean field calculations suggest that both shape coexistence and triaxiality are needed to describe these isotopes.

論文

Are there signatures of harmonic oscillator shells far from stability?; First spectroscopy of $$^{110}$$Zr

Paul, N.*; Corsi, A.*; Obertelli, A.*; Doornenbal, P.*; Authelet, G.*; 馬場 秀忠*; Bally, B.*; Bender, M.*; Calvet, D.*; Ch$^a$teau, F.*; et al.

Physical Review Letters, 118(3), p.032501_1 - 032501_7, 2017/01

 被引用回数:36 パーセンタイル:88.46(Physics, Multidisciplinary)

The first measurement of $$gamma$$ rays emitted by the very neutron rich nuclei $$^{112}$$Mo (Z=42) and $$^{110}$$Zr (Z=40) was carried out at the RIBF facility at RIKEN. These data shine light on the postulated N=70 harmonic oscillator shell. If the spin-orbit splitting which gives rise to the N=82 shell gap is reduced in very neutron-rich nuclei, the harmonic oscillator gap at N=70 should open instead. However, both the measured energy of the first excited state $$^{112}$$Mo and $$^{110}$$Zr, respectively 235(7) keV and 185(11) keV, and their E(4$$^+$$)/E(2$$^+$$) ratio, indicate that these nuclei are good rotors, and exclude the shell stabilization scenario at Z=40 and N=70. These results were compared to state-of-the-art density functional theoretical calculations using Gogny and Skyrme effective interactions.

論文

Spontaneous activation behavior of Ni$$_{3}$$Sn, an intermetallic catalyst, for hydrogen production via methanol decomposition

Fan, M.*; Xu, Y.*; 櫻井 惇也*; 出村 雅彦*; 平野 敏幸*; 寺岡 有殿; 吉越 章隆

International Journal of Hydrogen Energy, 40(37), p.12663 - 12673, 2015/10

 被引用回数:13 パーセンタイル:33.18(Chemistry, Physical)

Ni$$_{3}$$Sn単相粉末試料のメタノール分解反応に対する触媒特性を調べた。触媒反応は713K, 793K, 873Kの各温度で等温実験であった。793K以上の温度では触媒活性は時間の増加に伴い高くなることを見出した。また、Ni$$_{3}$$SnはH$$_{2}$$とCOに高い選択性を示すことが分かった。表面キャラクタリゼーションの結果、触媒反応中触媒表面にNi$$_{3}$$Sn微粒子が生成されることが分かった。これらの微粒子は自発活性化の原因と考えられる。

論文

In situ synthesis of volatile carbonyl complexes with short-lived nuclides

Even, J.*; Ackermann, D.*; 浅井 雅人; Block, M.*; Brand, H.*; Di Nitto, A.*; D$"u$llmann, Ch. E.*; Eichler, R.*; Fan, F.*; 羽場 宏光*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 303(3), p.2457 - 2466, 2015/03

 被引用回数:14 パーセンタイル:77.78(Chemistry, Analytical)

金属カルボニル錯体の迅速その場合成を、核分裂や核融合反応によって生成される短寿命同位体を用いた実験によって実証した。高い反跳エネルギーを持つ短寿命核反応生成物を一酸化炭素分子と直接反応させることでカルボニル錯体を合成し、高い揮発性を持つ錯体のみをガス気流によって迅速に搬送し、化学分析・測定装置にかけて検出した。この手法を用いることで、Mo, Tc, Ru, Rh, W, Re, Os, Irの短寿命同位体の揮発性カルボニル錯体の合成に成功した。一方、HfとTaの揮発性錯体は検出されなかった。この手法は超重元素シーボーギウム(原子番号106)の化学研究に既に適用されており、また短寿命遷移金属同位体を用いた核科学研究の様々な分野への応用が今後期待される。

論文

Synthesis and detection of a Seaborgium carbonyl complex

Even, J.*; Yakushev, A.*; D$"u$llmann, Ch. E.*; 羽場 宏光*; 浅井 雅人; 佐藤 哲也; Brand, H.*; Di Nitto, A.*; Eichler, R.*; Fan, F. L.*; et al.

Science, 345(6203), p.1491 - 1493, 2014/09

 被引用回数:60 パーセンタイル:83.09(Multidisciplinary Sciences)

超重元素の新しい錯体、106番元素シーボーギウム(Sg)のカルボニル錯体の合成に初めて成功し、その吸着特性を低温熱クロマトグラフィー・$$alpha$$線測定装置COMPACTを用いて調べた。理化学研究所の気体充填型反跳イオン分離装置GARISを用いて合成及び前段分離された短寿命核反応生成物$$^{265}$$Sgを、ヘリウムと一酸化炭素の混合ガス中に打ち込み、カルボニル錯体を合成した。生成したカルボニル錯体のうち揮発性の高いもののみをガス気流によってCOMPACTへと搬送し、低温熱クロマトグラフィー測定を行った。検出されたSgカルボニル錯体の吸着エンタルピーは-50kJ/molと求まり、この高い揮発性からこの錯体は6配位のSg(CO)$$_{6}$$であると結論した。これまで超アクチノイド元素では単純な無機錯体しか合成されたことがなく、本研究は超アクチノイド元素における初めての有機金属錯体合成の成果である。

論文

Catalytic performance of Ni$$_{3}$$Sn and Ni$$_{3}$$Sn$$_{2}$$ for hydrogen production from methanol decomposition

Fan, M.*; Xu, Y.*; 櫻井 惇也*; 出村 雅彦*; 平野 敏幸*; 寺岡 有殿; 吉越 章隆

Catalysis Letters, 144(5), p.843 - 849, 2014/05

 被引用回数:14 パーセンタイル:34.89(Chemistry, Physical)

In this study, the catalytic properties of Ni$$_{3}$$Sn and Ni$$_{3}$$Sn$$_{2}$$ powders were investigated for producing hydrogen from decomposing methanol in the temperatures from 593 to 953 K. The catalytic activities of Ni$$_{3}$$Sn and Ni$$_{3}$$Sn$$_{2}$$ both increased with increasing temperature, but Ni$$_{3}$$Sn showed much higher catalytic activity than Ni$$_{3}$$Sn$$_{2}$$. The results of an isothermal test performed at 873 K revealed that the catalytic activity of Ni$$_{3}$$Sn significantly increased with methanol decomposition time, indicating that Ni$$_{3}$$Sn was spontaneously activated. Ni$$_{3}$$Sn and Ni$$_{3}$$Sn$$_{2}$$ both showed a high degree of selectivity and both suppressed side reactions such as methanation and water-gas shift reaction. Surface analysis revealed that fine Ni-Sn particles were formed together with carbon deposited onto the catalyst surface. These Ni-Sn particles were supposed to serve as active sites for methanol decomposition.

論文

Anionic fluoro complex of element 105, Db

笠松 良崇*; 豊嶋 厚史; 浅井 雅人; 塚田 和明; Li, Z.; 石井 康雄; 當銘 勇人*; 佐藤 哲也; 菊池 貴宏; 西中 一朗; et al.

Chemistry Letters, 38(11), p.1084 - 1085, 2009/10

 被引用回数:14 パーセンタイル:49.01(Chemistry, Multidisciplinary)

105番元素ドブニウム(Db)のフッ化水素酸と硝酸混合水溶液中における陰イオン交換挙動を、新規に開発した迅速イオン交換分離装置を用いて調べた。Dbのフッ化物陰イオン錯体の挙動は、近接の第6周期同族元素タンタル(Ta)の挙動とは大きく異なり、第5周期のニオブ(Nb)の挙動と似ているという特徴的な性質を示すことがわかった。

口頭

Catalytic performance of Ni$$_{3}$$Sn alloy for hydrogen production from methanol decomposition

Fan, M.*; Xu, Y.*; 櫻井 惇也*; 出村 雅彦*; 平野 敏幸*; 寺岡 有殿; 吉越 章隆

no journal, , 

We have examined the catalytic performance of Ni$$_{3}$$Sn for hydrogen production from methanol decomposition. The single-phase Ni$$_{3}$$Sn alloy ingot was prepared using a high-frequency furnace. The ingot was mechanically crushed to powders. The powders were sieved to get the samples less than 75 micrometer in size for reaction test. Methanol decomposition was performed in a conventional fixed-bed flow reactor. The characterization of Ni$$_{3}$$Sn was carried out by XRD, SEM, BET, and synchrotron XPS in SPring-8. The methanol conversion increased with time indicating that Ni$$_{3}$$Sn spontaneously activated during the reaction. It was also found that Ni$$_{3}$$Sn shows a high selectivity. The characterization of the samples before and after reaction shows that Ni$$_{3}$$Sn phase remained unchanged, and no obvious oxidation of Ni and Sn occurred during reaction, suggesting that Ni$$_{3}$$Sn itself might serve as the active species.

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