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論文

New $$K$$ isomers in $$^{248}$$Cf

Orlandi, R.; 牧井 宏之; 西尾 勝久; 廣瀬 健太郎; 浅井 雅人; 塚田 和明; 佐藤 哲也; 伊藤 由太; 洲嵜 ふみ; 永目 諭一郎*; et al.

Physical Review C, 106(6), p.064301_1 - 064301_11, 2022/12

https://doi.org/10.1103/PhysRevC.106.064301
 被引用回数：0 パーセンタイル：0.02(Physics, Nuclear)

The nuclear structure of $$^{248}$$Cf produced by the $$^{18}$$O+$$^{249}$$Cf multinucleon transfer reaction was investigated using $$gamma$$-ray spectroscopy. Analysis of the $$gamma$$-ray spectrum of $$^{248}$$Cf revealed the presence of multiple long-lived (isomeric) excited states at low excitation energies. The energies and half-lives of the isomers contain information on the proton and neutron orbits in the heavy-element region and the deformation of atomic nuclei, and are important data to predict the properties of nuclei in the "island of stability".

論文

Measurement of 107-MeV proton-induced double-differential neutron yields for iron for research and development of accelerator-driven systems

岩元 大樹; 中野 敬太; 明午 伸一郎; 佐藤 大樹; 岩元 洋介; 石 禎浩*; 上杉 智教*; 栗山 靖敏*; 八島 浩*; 西尾 勝久; et al.

JAEA-Conf 2022-001, p.129 - 133, 2022/11

https://doi.org/10.11484/jaea-conf-2022-001

加速器駆動システム(ADS)の核特性予測精度の向上と京都大学臨界集合体実験装置(KUCA)におけるADS炉物理実験で用いる中性子源情報の取得を目的として、京都大学の固定磁場強集束(FFAG)加速器を用いた核データ測定実験プログラムを開始した。このプログラムの一環として、鉄に対する陽子入射二重微分中性子収量(TTNY)及び断面積(DDX)を測定した。測定では、真空チェンバ内に設置された鉄標的に107MeVの陽子ビームを照射し、核反応によって標的から発生した粒子の信号を、小型の中性子検出器を用いて検出した。検出信号とFFAGキッカー電磁石の信号の時間差から飛行時間(TOF)を求め、ガンマ線の事象を波形弁別法によって除去して中性子事象をカウントすることで中性子のTOFスペクトルを求めた。得られた中性子のTOFスペクトルから、相対論的運動学により鉄標的に対するTTNY及びDDXを求めた。

論文

Decay studies of new isomeric states in $$^{255}$$No

Bronis, A.*; He${ss}$berger, F. P.*; Antalic, S.*; Andel, B.*; Ackermann, D.*; Heinz, S.*; Hofmann, S.*; Khuyagbaatar, J.*; Kindler, B.*; Kojouharov, I.*; et al.

Physical Review C, 106(1), p.014602_1 - 014602_12, 2022/07

https://doi.org/10.1103/PhysRevC.106.014602
 被引用回数：0 パーセンタイル：0.02(Physics, Nuclear)

The decay of excited states in $$^{255}$$No was investigated by applying the evaporation-residue-conversion-electron correlation technique. Two new isomeric states were observed in $$^{255}$$No together with the previously known one. Excitation energies of the isomeric states were estimated based on the energies of conversion electrons and $$gamma$$ rays from correlation chains. These results were in accord with theoretical calculations based on the mean-field models. A tentative decay scheme of isomeric states in $$^{255}$$No is proposed, and their Nilsson configurations are discussed. The energy decrease of the 11/2$$^{-}$$[725] Nilsson level for heavy $$N$$=153 isotones as a function of increasing proton number is confirmed.

論文

Fission mechanism inferred from nuclear shape fluctuation by the Langevin equation

有友 嘉浩*; 岩本 昭*; 西尾 勝久; 太田 雅久*

Physical Review C, 105(3), p.034604_1 - 034604_8, 2022/03

https://doi.org/10.1103/PhysRevC.105.034604
 被引用回数：1 パーセンタイル：67.14(Physics, Nuclear)

One of the dynamical investigations for an understanding of the fission process is the analysis through Langevin trajectories in the nuclear deformation space. The main motivation of this analysis is to elucidate the characteristic nuclear-shape oscillation induced by a random force in the Langevin equation and its impact on the fission process. The characteristic random oscillation originates from the requirement of an overdamped condition. The properties of the friction tensor in the equation reveal that the directional nuclear shape fluctuations originate in the subspace of nuclear deformation. Our calculations exhibit a good agreement with the fission data for fermium isotopes, where the fission-fragment mass distribution changes dramatically from the asymmetric shape to the sharp symmetric shape as the masses of the fissioning Fm isotopes increase.

論文

Angular momentum transfer in multinucleon transfer channels of $$^{18}$$O + $$^{237}$$Np

田中 翔也*; 廣瀬 健太郎; 西尾 勝久; Kean, K. R.*; 牧井 宏之; Orlandi, R.; 塚田 和明; 有友 嘉浩*

Physical Review C, 105(2), p.L021602_1 - L021602_5, 2022/02

https://doi.org/10.1103/PhysRevC.105.L021602
 被引用回数：1 パーセンタイル：67.14(Physics, Nuclear)

The angular momentum of a primary excited compound nucleus produced in multinucleon transfer reaction is an important quantity to evaluate cross sections to synthesize neutron-rich heavy element nuclei as well as for surrogate reaction studies. The mechanism is, however, not enough understood due to the lack of detailed experimental data. In the present study, we determined the angular momentum of primary excited nuclei, $$^{237,238,239}$$Np, $$^{238,239,240}$$Pu, and $$^{239,240,241}$$Am, produced in the multi-nucleon transfer channels of the $$^{18}$$O + $$^{237}$$Np reaction. With this aim, angular distributions of fission fragments with respect to the axis perpendicular to the reaction plane were measured for each compound nucleus. The distributions show an anisotropy exhibiting an enhanced yield on the reaction plane. They are well reproduced by a saddle point model, from which the average angular momentum is derived in the model framework. The angular momentum increases with the compound-nucleus mass, thus the number of nucleons exchanged, but shows a saturating trend toward heavier compound nuclei. These results are the first ones to point to the dependence of the angular momentum on the transfer channels.

論文

Measurement of 107-MeV proton-induced double-differential thick target neutron yields for Fe, Pb, and Bi using a fixed-field alternating gradient accelerator at Kyoto University

岩元 大樹; 中野 敬太; 明午 伸一郎; 佐藤 大樹; 岩元 洋介; 杉原 健太; 西尾 勝久; 石 禎浩*; 上杉 智教*; 栗山 靖敏*; et al.

Journal of Nuclear Science and Technology, 15 Pages, 2022/00

https://doi.org/10.1080/00223131.2022.2115423
 被引用回数：0 パーセンタイル：0.01(Nuclear Science & Technology)

加速器駆動核変換システム(ADS)の研究開発及び京都大学臨界実験装置(KUCA)におけるADS未臨界炉物理の基礎研究を目的として、固定磁場強収束(FFAG)加速器を用いて107MeV陽子による鉄、鉛及びビスマス標的に対する二重微分中性子収量(TTNY)を測定した。TTNYは8個の中性子検出器(各検出器は小型のNE213液体有機シンチレータと光電子増倍管より構成される)からなる中性子検出器システムを用いて飛行時間法により得られたものである。測定で得られたTTNYを、粒子・重イオン輸送コードシステム(PHITS)に組み込まれたモンテカルロ法に基づく核破砕反応モデル(INCL4.6/GEM, Bertini/GEM, JQMD/GEM, JQMD/SMM/GEM)及び評価済み高エネルギー核データライブラリ(JENDL-4.0/HE)による計算結果と比較した。JENDL-4.0/HEを含む比較対象のモデルは、検出器角度5度における高エネルギーピークを再現しないなどの特徴的な不一致が見られた。測定で得られたTTNYとPHITSによって評価した20MeV以下のエネルギー及び角度積分中性子収率を比較した結果、INCL4.6/GEMがKUCAにおけるADS炉物理実験のモンテカルロ輸送シミュレーションに適していることが示された。

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

https://doi.org/10.3847/1538-4357/ac12ce
 被引用回数：1 パーセンタイル：17.16(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

Chemical characterization of a volatile dubnium compound, DbOCl$$_3$$

Chiera, N. M.*; 佐藤 哲也; Eichler, R.*; 富塚 知博; 浅井 雅人; 安達 サディア*; Dressler, R.*; 廣瀬 健太郎; 井上 浩樹*; 伊藤 由太; et al.

Angewandte Chemie; International Edition, 60(33), p.17871 - 17874, 2021/08

https://doi.org/10.1002/anie.202102808
 被引用回数：2 パーセンタイル：30.08(Chemistry, Multidisciplinary)

等温ガスクロマトグラフ法を用いて、105番元素ドブニウム(Db)の単一原子を対象として、揮発性オキシ塩化物を合成し、化学的性質を調べた。同一条件下で同族元素ニオブおよびタンタルの揮発性と比較したところ、NbOCl$$_3 > $$ TaOCl$$_3 geq$$ DbOCl$$_3$$の関係が得られた。これはDb分子中の共有結合性が周期表からの予想よりも強くなっているためと考えられる。本成果により、超アクチノイド元素の化学的性質に関する理論計算に対する信頼できる実験データを与えることができた。

論文

Experimental study of the $$Gamma_{p1}/Gamma_{p0}$$ ratios of resonance states in $$^{8}$$Be for deducing the $$^{7}$$Be($$n$$,$$p_{1}$$)$$^{7}$$Li$$^{*}$$ reaction rate relevant to the cosmological lithium problem

岩佐 直仁*; 石川 竣喜*; 久保野 茂*; 榊原 昂浩*; 小湊 和也*; 西尾 勝久; 松田 誠; 廣瀬 健太郎; 牧井 宏之; Orlandi, R.; et al.

Physical Review C, 103(1), p.015801_1 - 015801_5, 2021/01

https://doi.org/10.1103/PhysRevC.103.015801
 被引用回数：1 パーセンタイル：32.08(Physics, Nuclear)

The $$^{9}$$Be($$^{3}$$He,$$alpha$$)$$^{8}$$Be($$p$$)$$^{7}$$Li reaction was studied at $$E_{rm lab}$$($$^{3}$$He)=30 MeV to deduce the branching ratios of $$Gamma_{p1}/Gamma_{p0}$$ of resonant state at 18.91 - 20.1 MeV in $$^{8}$$Be, which are necessary to extract the $$^{7}$$Be($$n$$, $$p_{1}$$)$$^{7}$$Li$$^{*}$$ reaction rate relevant to the $$^{7}$$Be destruction in the big bang nucleosynthesis, from the $$^{7}$$Li($$p$$,$$n_{0}$$)$$^{7}$$Be reaction cross section. The decay protons from $$^{8}$$Be$$^{*}$$ to the ground and first excited states in $$^{7}$$Li were well-separately measured. The $$Gamma_{p1}/Gamma_{p0}$$ ratio of the 19.235-MeV state was deduced to be 3.4$$pm$$1.9%. The 19.86- and 20.1-MeV states were found to decay dominantly into the first excited and ground states of $$^{7}$$Li, respectively.

論文

Measurement of fission-fragment mass distributions in the multinucleon transfer channels of the $$^{18}$$O+$$^{237}$$Np reaction

Vermeulen, M. J.; 西尾 勝久; 廣瀬 健太郎; Kean, K. R.; 牧井 宏之; Orlandi, R.; 塚田 和明; Tsekhanovich, I.*; Andreyev, A. N.; 石崎 翔馬*; et al.

Physical Review C, 102(5), p.054610_1 - 054610_11, 2020/11

https://doi.org/10.1103/PhysRevC.102.054610
 被引用回数：4 パーセンタイル：56.79(Physics, Nuclear)

Fission fragment mass distributions for 23 nuclei ($$^{234-237}$$U, $$^{236-239}$$Np, $$^{238-241}$$Pu, $$^{240-243}$$Am, $$^{242-245}$$Cm, and $$^{244-246}$$Bk) were measured using the multi-nucleon transfer approach in the reaction of $$^{18}$$O+$$^{237}$$Np, and their excitation-energy dependence was obtained up to a maximum of 70 MeV. Among them, the low energy fission of $$^{236}$$Np, $$^{238}$$Pu, and $$^{245}$$Cm is reported for the first time. The experimental data for all the studied nuclei were compared to the Langevin calculations. The calculation which takes into account the effects of multi-chance fission well reproduced the peak-to-valley ratio and mass-asymmetric peak positions of the distributions. The angular momenta given to the fissioning nucleus is also discussed.

論文

フェルミウム原子核で起きるユニークな核分裂; 動力学模型の視点から

有友 嘉浩*; 宮本 裕也*; 西尾 勝久

日本物理学会誌, 75(10), p.631 - 636, 2020/10

フェルミウム元素(Fm, 原子番号100)の核分裂において、1980年代の実験で興味深い結果が報告された。$$^{257}$$Fmから$$^{258}$$Fmへと原子核の質量数が1つ変化しただけで、ウランで見られるような質量非対称核分裂から、シャープな質量対称核分裂へと変化した。この変化の原因を説明するため多くの理論モデルが提案されてきたが、実験データを定量的に説明できる模型はなかった。本研究では、ランジュバンモデルを用いた動力学計算を行うことにより、この変化の原因を説明することができた。このモデルの構築のため、原子力科学研究所タンデム加速器で測定した核分裂データを使用した。核分裂の発見と理論の歴史を概説しつつ、Fmで起こる現象について分かりやすく解説した。

論文

$$alpha$$ decay of $$^{243}$$Fm$$_{143}$$ and $$^{245}$$Fm$$_{145}$$, and of their daughter nuclei

Khuyagbaatar, J.*; He${ss}$berger, F. P.*; Hofmann, S.*; Ackermann, D.*; Burkhard, H. G.*; Heinz, S.*; Kindler, B.*; Kojouharov, I.*; Lommel, B.*; Mann, R.*; et al.

Physical Review C, 102(4), p.044312_1 - 044312_8, 2020/10

https://doi.org/10.1103/PhysRevC.102.044312
 被引用回数：5 パーセンタイル：65.07(Physics, Nuclear)

Nuclear structure of $$^{243}$$Fm, $$^{245}$$Fm, and their daughter nuclei were investigated via detection of their radioactive decays, $$alpha$$, $$gamma$$, and spontaneous fission. Measured $$alpha$$-decay energies, half-lives, and branching ratios improve the literature data significantly. A signature for detection of the hitherto unknown $$^{235}$$Cm was found in the $$alpha$$-decay chains from $$^{243}$$Fm. Two groups of $$alpha$$ events with average energies of 6.69(2) MeV and 7.01(2) MeV and with a half-life of $$T_{1/2}$$ = 300$$^{+250}_{-100}$$, s are suggested to originate from $$^{235}$$Cm. Tentative decay schemes for $$^{243}$$Fm, $$^{239}$$Cf, $$^{235}$$Cm, and $$^{245}$$Fm, $$^{241}$$Cf isotopes are suggested based on the present experimental data. Systematical trends of single-particle states in $$N$$=141 isotones of $$Z$$ = 92-98 nuclei are discussed.

論文

Simultaneous determination of neutron-induced fission and radiative capture cross sections from decay probabilities obtained with a surrogate reaction

P$'e$rez S$'a$nchez, R.*; Jurado, B.*; M$'e$ot, V.*; Roig, O.*; Dupuis, M.*; Bouland, O.*; Denis-Petit, D.*; Marini, P.*; Mathieu, L.*; Tsekhanovich, I.*; et al.

Physical Review Letters, 125(12), p.122502_1 - 122502_5, 2020/09

https://doi.org/10.1103/PhysRevLett.125.122502
 被引用回数：4 パーセンタイル：48.03(Physics, Multidisciplinary)

Reliable neutron-induced-reaction cross sections of unstable nuclei are essential for nuclear astrophysics and applications but their direct measurement is often impossible. The surrogate-reaction method is one of the most promising alternatives to access these cross sections. In this work, we successfully applied the surrogate-reaction method to infer for the first time both the neutron-induced fission and radiative capture cross sections of $$^{239}$$Pu in a consistent manner from a single measurement. This was achieved by combining simultaneously measured fission and $$gamma$$-emission probabilities for the $$^{240}$$Pu($$^{4}$$He, $$^{4}$$He') surrogate reaction with a calculation of the angular-momentum and parity distributions populated in this reaction. While other experiments measure the probabilities for some selected $$gamma$$-ray transitions, we measure the $$gamma$$-emission probability. This enlarges the applicability of the surrogate-reaction method.

論文

Production of $$^{266}$$Bh in the $$^{248}$$Cm($$^{23}$$Na,5$$n$$)$$^{266}$$Bh reaction and its decay properties

羽場 宏光*; Fan, F.*; 加治 大哉*; 笠松 良崇*; 菊永 英寿*; 小森 有希子*; 近藤 成美*; 工藤 久昭*; 森本 幸司*; 森田 浩介*; et al.

Physical Review C, 102(2), p.024625_1 - 024625_12, 2020/08

https://doi.org/10.1103/PhysRevC.102.024625
 被引用回数：5 パーセンタイル：56.79(Physics, Nuclear)

The nuclide $$^{266}$$Bh was produced in the $$^{248}$$Cm($$^{23}$$Na,5n)$$^{266}$$Bh reaction at beam energies of 125.9, 130.6, and 135.3 MeV. Decay properties of $$^{266}$$Bh were investigated with a rotating wheel apparatus for $$alpha$$ and spontaneous fission (SF) spectrometry under low background conditions attained by a gas-jet transport system coupled to the RIKEN gas-filled recoil ion separator. The half-life of $$^{266}$$Bh was measured to be $$T_{rm 1/2}$$ = 10.0$$^{+2.6}_{-1.7}$$ s. The $$alpha$$-particle energies of $$^{266}$$Bh disperse widely in the range of 8.62 - 9.40 MeV. The maximum production cross section for the $$^{248}$$Cm($$^{23}$$Na,5n)$$^{266}$$Bh reaction was determined to be $$sigma$$ = 57 $$pm$$ 14 pb at 130.6 MeV.

論文

Estimation of synthesizing new superheavy elements using dynamical model

有友 嘉浩*; 天野 翔太*; 奥林 瑞貴*; 栁 漠*; 西尾 勝久; 太田 雅久*

Physics of Atomic Nuclei, 83(4), p.545 - 549, 2020/07

https://doi.org/10.1134/S1063778820040043
 被引用回数：0 パーセンタイル：0.02(Physics, Nuclear)

For the success of synthesis of the superheavy elements Z $$>$$ 118, it is indispensable to clarify the fusion-fission mechanism, which includes a role of the nuclear structure of colliding nuclei and the deformation in the fusion process. We develop the dynamical model to estimate the probability to produce new superheavy nuclei. To approach Island of Stability and synthesize new elements, we propose a new idea, which takes advantage of the shell structure in fusion and fission process.

論文

Study of quasielastic barrier distributions as a step towards the synthesis of superheavy elements with hot fusion reactions

田中 泰貴*; 森田 浩介*; 森本 幸司*; 加治 大哉*; 羽場 宏光*; Boll, R. A.*; Brewer, N. T.*; Van Cleve, S.*; Dean, D. J.*; 石澤 倫*; et al.

Physical Review Letters, 124(5), p.052502_1 - 052502_6, 2020/02

https://doi.org/10.1103/PhysRevLett.124.052502
 被引用回数：12 パーセンタイル：74.3(Physics, Multidisciplinary)

The excitation functions for quasielastic scattering of $$^{22}$$Ne+$$^{248}$$Cm, $$^{26}$$Mg+$$^{248}$$Cm, $$^{48}$$Ca+$$^{238}$$U are measured using a gas-filled recoil ion separator The quasielastic barrier distributions are extracted for these systems and are compared with coupled-channel calculations. The results indicate that the barrier distribution is affected dominantly by deformation of the actinide target nuclei, but also by vibrational or rotational excitations of the projectile nuclei, as well as neutron transfer processes before capture. From a comparison between the experimental barrier distributions and the evaporation residue cross sections for Sg (Z=106), Hs (108), Cn (112), and Lv (116), it is suggested that the hot fusion reactions take advantage of a compact collision, where the projectile approaches along the short axis of a prolately deformed nucleus. A new method is proposed to estimate the optimum incident energy to synthesize unknown superheavy nuclei using the barrier distribution.

論文

New excited 2$$^+$$ and 3$$^-$$ two-proton states in $$_{84}^{210}$$Po$$_{126}$$ populated by two-proton transfer

Dupont, E.*; Astier, A.*; Petrache, C. M.*; Lv, B. F.*; Deloncle, I.*; Kiener, J.*; Orlandi, R.; 牧井 宏之; 西尾 勝久; 廣瀬 健太郎; et al.

Physical Review C, 101(1), p.014309_1 - 014309_6, 2020/01

https://doi.org/10.1103/PhysRevC.101.014309
 被引用回数：1 パーセンタイル：18.5(Physics, Nuclear)

Five new 2$$^+$$ levels and one new 3$$^-$$ level were established in $$^{210}$$Po. The states were populated via the $$^{208}$$Pb($$^{12}$$C, $$^{10}$$Be) two-proton reaction experiment, performed at the JAEA Tandem in Tokai. A setup combining Ge, LaBr$$_3$$, and Si telescopes was used to detect in-beam $$gamma$$-rays and ejectile residues. Two-proton configurations were assigned to all new states. All assignments are strongly supported by shell-model calculations.

論文

Effects of multichance fission on isotope dependence of fission fragment mass distributions at high energies

田中 翔也; 有友 嘉浩*; 宮本 裕也*; 廣瀬 健太郎; 西尾 勝久

Physical Review C, 100(6), p.064605_1 - 064605_6, 2019/12

https://doi.org/10.1103/PhysRevC.100.064605
 被引用回数：7 パーセンタイル：67.6(Physics, Nuclear)

散逸揺動定理を採用した動力学模型を使用し、$$^{234-240}$$U, $$^{236-242}$$Np, $$^{238-244}$$Pu ($$E^{*}$$=15-55MeV)という広い範囲の核種および励起エネルギーにおいて核分裂片質量分布の評価を行った。本研究の特色は、原子核が分裂へ至るまでに中性子を放出するという、マルチチャンス核分裂の概念を理論計算へ導入していることである。その結果、実験データを系統的に再現する計算結果を得られた。特に、励起エネルギーが高い領域においても核分裂片質量分布がふた山構造を維持する傾向や、原子核の初期状態(特に中性子数)に依存するという実験データの傾向を再現することに成功した。またこの傾向が、核分裂前の中性子放出確率を支配している複合核の中性子結合エネルギーと相関を持つことを示した。

論文

$$alpha$$-decay properties of $$^{200,202}$$Fr

Ghys, L.*; Andreyev, A. N.; Huyse, M.*; Van Duppen, P.*; Antalic, S.*; Barzakh, A.*; Capponi, L.*; Cocolios, T. E.*; Cubiss, J.*; Derkx, X.*; et al.

Physical Review C, 100(5), p.054310_1 - 054310_13, 2019/11

https://doi.org/10.1103/PhysRevC.100.054310
 被引用回数：11 パーセンタイル：81.7(Physics, Nuclear)

The aim of this work was to investigate the $$alpha$$-decay properties of $$^{200,202}$$Fr and daughter products. Neutron-deficient francium nuclei are produced at ISOLDE-CERN bombarding a UCx target with 1.4 GeV protons. Due to the very high statistics and the high beam purity, improved decay data for $$^{202}$$Fr and its daughters were obtained. The observation of crossover transitions positioned the isomeric high-spin level of $$^{198}$$At at an excitation energy of 265(3) keV. Half-life values of 4.47(5) s and 1.28(10) s were extracted for the ground state and isomeric state of $$^{198}$$At and 52(3) ms for the ground-state decay of $$^{200}$$Fr.

論文

Effects of the nuclear structure of fission fragments on the high-energy prompt fission $$gamma$$-ray spectrum in $$^{235}$$U($$n_{rm th},f$$)

牧井 宏之; 西尾 勝久; 廣瀬 健太郎; Orlandi, R.; L$'e$guillon, R.; 小川 達彦; Soldner, T.*; K$"o$ster, U.*; Pollitt, A.*; Hambsch, F.-J.*; et al.

Physical Review C, 100(4), p.044610_1 - 044610_7, 2019/10

https://doi.org/10.1103/PhysRevC.100.044610
 被引用回数：10 パーセンタイル：78.79(Physics, Nuclear)

The prompt fission $$gamma$$-ray energy spectrum for cold-neutron induced fission of $$^{235}$$U was measured in the energy range $$E_{rm gamma}$$ = 0.8 - 20,MeV, by gaining a factor of about 10$$^{5}$$ in statistics compared to the measurements performed so far. The spectrum exhibits local bump structures at $$E_{rm gamma}approx$$4,MeV and $$approx$$6,MeV, and also a broad one at $$approx$$15,MeV. In order to understand the origins of these bumps, the $$gamma$$-ray spectra were calculated using a statistical Hauser-Feshbach model, taking into account the de-excitation of all the possible primary fission fragments. It is shown that the bump at $$approx$$4,MeV is created by the transitions between the discrete levels in the fragments around $$^{132}$$Sn, and the bump at $$approx$$6,MeV mostly comes from the complementary light fragments. It is also indicated that a limited number of nuclides, which have high-spin states at low excitation energies, can contribute to the bump structure around $$E_{rm gamma}approx$$15,MeV, induced by the transition feeding into the low-lying high-spin states.

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