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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:1 パーセンタイル:100(Physics, Nuclear)中性子過剰核であるCoに対する(
)ノックアウト反応が理化学研究所RIBFで測定された。
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、
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。
園田 哲*; 片山 一郎*; 和田 道治*; 飯村 秀紀; Sonnenschein, V.*; 飯村 俊*; 高峰 愛子*; Rosenbusch, M.*; 小島 隆夫*; Ahn, D. S.*; et al.
Progress of Theoretical and Experimental Physics (Internet), 2019(11), p.113D02_1 - 113D02_12, 2019/11
被引用回数:0 パーセンタイル:100(Physics, Multidisciplinary)理化学研究所の不安定核ビーム施設(RIBF)では、入射核破砕反応や核分裂で生成される多くの核種からインフライト分離装置(BigRIPS)を用いて実験対象の核種を分離している。しかるに、分離された残りの核反応生成物の中にも核構造から興味深い多くの不安定核が含まれている。これらをBigRIPSから取り出して研究することができれば、RIBFの有効利用につながる。そこで、BigRIPS内に設置したガスセル中で核反応生成物を停止させてレーザーでイオン化して引き出す装置(PALIS)を開発中である。開発の一環として、RIBFのKrビームの破砕反応により生成する
Se近傍の不安定核をガスセル中で停止させる実験を行なった。実験結果は破砕反応の模型計算の予測とよく一致し、ガスセル中での停止効率は約30%と評価された。この結果を基に、次のステップとして、停止した核反応生成物をガスセルから引き出すことを行う。
渡邉 寛*; Wang, H. K.*; Lorusso, G.*; 西村 俊二*; Xu, Z. Y.*; 炭竃 聡之*; Orlandi, R.; 他47名*
Physics Letters B, 792, p.263 - 268, 2019/05
被引用回数:1 パーセンタイル:63.02(Astronomy & Astrophysics)The isotopes Pd and
Pd, respectively with 79 and 81 neutrons, are key isotopes to understand the evolution of the N=82 shell closure below
Pd. These nuclei were studied at RIBF (RIKEN). New isomeric states with half-lives of 144(4) ns and 39(6)
s were assigned spins and parities of (23/2
) and (19/2
) in
Pd and
Pd, respectively. The assignment was carried out based on the results of the
-ray intensity balance analysis and the measured transition strengths with the aid of a shell-model calculation. The isomoer in
Pd was ascribed predominantly to three neutron-hole excitations in the N=50-82 shell. The 19/2
state in
Pd is expected to involve the coupling of proton and neutron configurations. The new data will provide important benchmarks for a better understanding of
-process nucleosynthesis.
Elekes, Z.*; Kripk,
*; 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:3 パーセンタイル:27.46(Physics, Nuclear)(,
)反応による
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。
Shand, C. M.*; Podolyk, Zs.*; G
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:13 パーセンタイル:13.18(Astronomy & Astrophysics)Low-lying states in neutron-rich Zn nuclei were measured for the first time via in-beam
-ray spectroscopy at RIKEN. These include the 4
to 2
in
Zn and the 2
to 0
and 4
to 2
in
Zn. The reduced E(
) energies and increased E(4
)/E(2
) ratios at
=52,54 compared to
Zn attest that the magicity is confined just on the neutron number
=50 only. The levels observed in
Zn suggest the onset of deformation towards heavier Zn isotopes. The data were compared to state-of-the-art shell model calculations.
Jungclaus, A.*; Grawe, H.*; 西村 俊二*; Doornenbal, P.*; Lorusso, G.*; Simpson, G. S.*; Sderstr
m, P.-A.*; 炭竃 聡之*; Taprogge, J.*; Xu, Z. Y.*; et al.
Physics Letters B, 772, p.483 - 488, 2017/09
被引用回数:6 パーセンタイル:34.59(Astronomy & Astrophysics)A new high-spin isomer in the neutron-rich nucleus Cd was populated in the projectile fission of a
U beam at the Radioactive Isotope Beam Factory at RIKEN. A half-life of T
= 6.3(8) ms was measured for the new state which was tentatively assigned a spin/parity of (15
). The isomeric state decays via the emission of a 309-keV
ray with
multipolarity. The experimental results are compared to shell model calculations performed using state-of-the-art realistic effective interactions and to the neighbouring nucleus
Cd. The comparison with calculations shows that adjustments of the pairing and multipole parts of the effective interaction derived from the CD-Bonn nucleon-nucleon potential are required in order to describe the properties of nuclei in the region around
Sn.
Morales, A. I.*; Benzoni, G.*; Watanabe, H.*; 角田 佑介*; Otsuka, T.*; 西村 俊二*; Browne, F.*; Daido, R.*; Doornenbal, P.*; Fang, Y.*; et al.
Physics Letters B, 765, p.328 - 333, 2017/02
被引用回数:21 パーセンタイル:6.23(Astronomy & Astrophysics)The level schemes of neutron-rich isotopes Co and
Ni were populated in the
decay of
Fe and studied using
-delayed
-ray spectroscopy of the
decay, at the RIBF in RIKEN, Japan. The experimental results were compared to state-of-the-art shell-model calculations, and indicate a dominance of prolate deformation in the low-lying states, coexisting with spherical states. The
decay of the
isobars is shown to progress in accordance to a new type of shell evolution, the so-called Type II, which involves many particle-hole excitations across energy gaps.
Jungclaus, A.*; Grawe, H.*; 西村 俊二*; Doornenbal, P.*; Lorusso, G.*; Simpson, G. S.*; Sderstr
m, P. A.*; 炭竃 聡之*; Taprogge, J.*; Xu, Z. Y.*; et al.
Physical Review C, 94(2), p.024303_1 - 024303_8, 2016/08
被引用回数:14 パーセンタイル:17.57(Physics, Nuclear)The decay of the semi-magic nucleus
Cd has been studied at the RIBF facility at the RIKEN Nishina Center. The high statistics of the present experiment allowed for a revision of the established level scheme of
In and the observation of additional
feeding to high lying core-excited states in
In. The experimental results are compared to shell-model calculations employing a model space consisting of the full major
neutron and
proton shells, and good agreement is found.
Jungclaus, A.*; Gargano, A.*; Grawe, H.*; Taprogge, J.*; 西村 俊二*; Doornenbal, P.*; Lorusso, G.*; Shimizu, Y.*; Simpson, G. S.*; Sderstr
m, P.-A.*; et al.
Physical Review C, 93(4), p.041301_1 - 041301_6, 2016/04
被引用回数:15 パーセンタイル:16.06(Physics, Nuclear)For the first time, the decay of excited states in a nucleus situated "south-east" of Sn have been observed, in a region where experimental information is limited to ground-state properties. Six
rays from
Cd, produced in the fragmentation of a
U beam at RIBF at RIKEN. The
rays were studied using the EURICA array of Ge detectors. The new experimental information is compared to results from realistic shell-model calculations, which are the first in this region far from stability. Comparison with calculations suggests that at least four out of six new transitions can be attributed to the particle-hole configuration of one neutron in the
and one proton hole in the
orbits, respectively. This work constitutes an important first step towards the exploration of nuclear structure in this unknown region of the nuclear chart.
Morales, A. I.*; Benzoni, G.*; Watanabe, H.*; 西村 俊二*; Browne, F.*; Daido, R.*; Doornenbal, P.*; Fang, Y.*; Lorusso, G.*; Patel, Z.*; et al.
Physical Review C, 93(3), p.034328_1 - 034328_14, 2016/03
被引用回数:16 パーセンタイル:16.06(Physics, Nuclear)Low-lying excited states in Ni have been investigated at RIKEN by studying the
decay of
Co to
Ni.
Co was separated with BigRIPS, implanted into the WaS3ABi Silicon array, and the
ray measured using the EURICA
spectrometer. From the analysis, 60 new
-ray transitions and 21 new levels in
Ni were observed. The new experimental information is compared to shell-model calculations which include neutron excitation across the
shell. The calculations reproduce rather well the observed states, implying that a clear understanding of these low-lying excitations has been achieved.
Benzoni, G.*; Morales, A. I.*; Watanabe, H.*; 西村 俊二*; Coraggio, L.*; Itaco, N.*; Gargano, A.*; Browne, F.*; Daido, R.*; Doornenbal, P.*; et al.
Physics Letters B, 751, p.107 - 112, 2015/12
被引用回数:14 パーセンタイル:21.8(Astronomy & Astrophysics)The decays of
Mn have been measured at the RIBF facility at RIKEN using the EURICA
spectrometer combined with an active stopper consisting of a stack of Si detectors. Half-lives and
-delayed neutron emission probabilities have been extracted for these decays, together with first experimental information on excited states populated in
Fe. The data indicate a continuously increasing deformation for Fe isotopes up to A=70, and interpreted to be due to the interplay between quadrupole correlation of specific neutron orbitals and the monopole component of the proton-neutron interaction.
Steiger, K.*; 西村 俊二*; Li, Z.*; Gernhuser, R.*; 宇都野 穣; Chen, R.*; Faestermann, T.*; Hinke, C.*; Kr
cken, R.*; 西村 美月*; et al.
European Physical Journal A, 51(9), p.117_1 - 117_9, 2015/09
被引用回数:6 パーセンタイル:47.75(Physics, Nuclear)中性子数20領域の中性子過剰核では、魔法数20が消滅することが知られ、殻構造の変化が起きていると考えられている。この論文では、この領域の殻構造をより直接的に調べるため、Si核の準位構造を
Al核のベータ崩壊によって調べた結果を報告する。
Alを理化学研究所RIBFを用いて生成し、そこからのベータ崩壊後の
線を観測することによって、
Si核の低励起状態の準位構造を得た。
Siの717keVと1270keVに強く遷移することから、これらの準位は正パリティ状態と同定された。実験で得られた準位構造は殻模型計算によってよく再現され、717keVと1270keVはそれぞれ
,
に対応することがわかった。この結果は、最近の殻模型相互作用が与える殻構造変化を確かめるものである。
Taprogge, J.*; Jungclaus, A.*; Grawe, H.*; 西村 俊二*; Doornenbal, P.*; Lorusso, G.*; Simpson, G. S.*; Sderstr
m, P.-A.*; 炭竃 聡之*; Xu, Z. Y.*; et al.
Physical Review C, 91(5), p.054324_1 - 054324_11, 2015/05
被引用回数:22 パーセンタイル:11.23(Physics, Nuclear)The decay of
Cd, produced in relativistic fission of a
U beam, was studied at the RIKEN Nishina Center. From the
-ray analysis, 31 excited states and 69
ray transitions were established in the level scheme of
In, and compared with state-of-the-art shell-model calculations. It was found that the
decay of
Cd is dominated by Gamow teller transitions, but a non-negligible contribution to the
decay is also made by first-forbidden transitions. To estimate the contribution of first-forbidden transitions is important for calculations of the
-decay half-lives of nuclei in this region.
Lorusso, G.*; 西村 俊二*; Xu, Z. Y.*; Jungclaus, A.*; Shimizu, Y.*; Simpson, G. S.*; Sderstr
m, P.-A.*; Watanabe, H.*; Browne, F.*; Doornenbal, P.*; et al.
Physical Review Letters, 114(19), p.192501_1 - 192501_7, 2015/05
被引用回数:104 パーセンタイル:1.9(Physics, Multidisciplinary)The -decay half-lives of 110 neutron-rich isotopes of the elements from Rb to Sn were measured at the RIBF Facility at RIKEN, Japan. The new data demonstrate the persistence of shell structure far from stability and have direct implications for the
-process calculations. In particular, the new half-lives have a global impact on the calculated
-process elemental abundances, and alleviate the underproduction of isotopes just above and below the A=130 peak, which in the past required the introduction of shell structure modifications. Reaction-network calculations based on the new data reinforce the notion that the r-process abundance pattern may result from the freeze-out of a (n,
)
(
,n) equilibrium.
Taprogge, J.*; Jungclaus, A.*; Grawe, H.*; 西村 俊二*; Xu, Z. Y.*; Doornenbal, P.*; Lorusso, G.*; Ncher, E.*; Simpson, G. S.*; S
derstr
m, P.-A.*; et al.
Physics Letters B, 738, p.223 - 227, 2014/11
被引用回数:17 パーセンタイル:19.79(Astronomy & Astrophysics)The decay of an isomeric state in the neutron-rich nucleus Cd was observed via the detection of internal conversion and Compton electrons. This measurement provided the first experimental information on excited states in this nucleus. The isomer was populated in the projectile fission of a
U beam at the RIBF facility at RIKEN. From the measured yields of
rays and internal conversion electrons, E3 multipolarity was tentatively assigned to the isomeric transition. A half-life of 3.6(2) ms was determined for this new state which, by comparison with shell-model calculations, was tentatively assigned a spin of (21/2
).
Simpson, G. S.*; Gey, G.*; Jungclaus, A.*; Taprogge, J.*; 西村 俊二*; Sieja, K.*; Doornenbal, P.*; Lorusso, G.*; Sderstr
m, P.-A.*; 炭竃 聡之*; et al.
Physical Review Letters, 113(13), p.132502_1 - 132502_6, 2014/09
被引用回数:48 パーセンタイル:7.65(Physics, Multidisciplinary)Delayed -ray cascades, originating from the decay of 6
isomeric states, in the very neutron-rich, semimagic isotopes
Sn were observed following the projectile fission of a
U beam at RIBF, RIKEN. The wave functions of these isomeric states are proposed to be predominantly a fully aligned pair of f
neutrons. Shell-model calculations, performed using a realistic effective interaction, reproduce well the energies of the excited states of these nuclei and the measured transition rates, with the exception of the
2;6
) rate of
Sn, which deviates from a simple seniority scheme. Empirically reducing the
orbit matrix elements produces a 4+1 state with almost equal seniority 2 and 4 components, correctly reproducing the experimental
2;6
) rate of
Sn. These data provide a key benchmark for shell-model interactions far from stability.
Watanabe, H.*; Lorusso, G.*; 西村 俊二*; Otsuka, T.*; Ogawa, K.*; Xu, Z. Y.*; 炭竃 聡之*; Sderstr
m, P.-A.*; Doornenbal, P.*; Li, Z.*; et al.
Physical Review Letters, 113(4), p.042502_1 - 042502_6, 2014/07
被引用回数:19 パーセンタイル:21.23(Physics, Multidisciplinary)A new isomer with a half-life of 23.0(8) ms has been identified in Pd at 2406 keV excitation. The proposed spin and parity configuration is 10
, with maximally aligned configuration of two
neutron hole.
-decay from the long-lived isomer was also observed to populated excited states at high spins in
Ag. The small energy difference between the 10
and 7
isomers in
Pd was interpreted in the frame of the monopole shift of the 1
neutron orbit. The effects of the monopole interaction on the evolution of single-neutron energies below
Sn are discussed in terms of central and tensor forces.
Taprogge, J.*; Jungclaus, A.*; Grawe, H.*; 西村 俊二*; Doornenbal, P.*; Lorusso, G.*; Simpson, G.*; Sderstr
m, P.-A.*; 炭竃 聡之*; Xu, Z. Y.*; et al.
Physical Review Letters, 112(13), p.132501_1 - 132501_6, 2014/04
被引用回数:43 パーセンタイル:9.29(Physics, Multidisciplinary)A low-lying state in In, the one-proton hole nucleus with respect to double magic
Sn, was observed by its
decay to the beta emitting isomer. The new state, which was populated both in the beta decay of
Cd and after beta-delayed neutron emission from
Cd, was identified, at an excitation energy of 1353 keV, as the previously unknown single-hole state with respect to the
Sn core. Exploiting this crucial new experimental information, shell-model calculations were performed to study the structure of experimentally inaccessible
=82 isotones below
Sn. The results evidence a surprising absence of proton subshell closures along the chain of
=82 isotones. This finding bears consequences on the evolution of the
=82 shell gap along the r-process path.
久保野 茂*; 寺西 高*; 野谷 将広*; 山口 英斉*; 齋藤 明登*; He, J. J.*; 若林 泰生*; 藤川 尚志*; Amadio, G.*; 馬場 秀忠*; et al.
Nuclear Physics A, 758, p.733 - 736, 2005/07
CRIBからの短寿命核ビームを用いて陽子非弾性散乱を測定した。これにより爆発的水素燃焼過程を理解するうえで重要な
における共鳴状態の核物理パラメタを求めた。
ビームによる非弾性散乱実験の結果も合わせて報告する。
若林 泰生; 山口 英斉*; 橋本 尚志*; 早川 勢也*; 栗原 佑蔵*; Binh, D.*; Kahl, D.*; 久保野 茂*; 西村 俊二*; 郷農 靖之*; et al.
no journal, ,
For the rapid proton capture process (-process) in X-ray bursts and the core-collapse stage of supernovae, proton-rich
-shell nuclei far from the line of stability play important roles. Studies of the feeding ratios and half-lives of the
and electron capture decays of these proton-rich
-shell nuclei are of great astrophysical interest not only for nucleosynthesis but also for Fermi and Gamow-Teller transition study. The experiment to measure the half life of
decay of
Cr was performed using the low-energy RI beam separator (CRIB) of the Center for Nuclear Study (CNS), University of Tokyo. The
Cr particles were produced by the
Ar +
C fusion reaction. A natural C foil of 0.56 mg/cm
was installed as the primary target. The
Ar primary beam was accelerated up to 3.6 MeV/nucleon by the RIKEN AVF cyclotron. A double sided Si strip detector (DSSD) of 500-
m thickness was used as a
-ray detector. A Si detector of 1.5-mm thickness was placed just behind the DSSD for a
-ray detector. To measure
-delayed
rays, 3 clover and 1 coaxial Ge detectors were set around the target chamber. The beam was pulsed to measure the half life of the
decay of
Cr. The
-delayed
ray of
Cr was observed in this experiment. The experimental result will be discussed.