Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
飯村 俊*; Rosenbusch, M.*; 高峰 愛子*; 角田 佑介*; 和田 道治*; Chen, S.*; Hou, D. S.*; Xian, W.*; 石山 博恒*; Yan, S.*; et al.
Physical Review Letters, 130(1), p.012501_1 - 012501_6, 2023/01
被引用回数:6 パーセンタイル:93.39(Physics, Multidisciplinary)The atomic masses of Sc, Ti, and V have been determined using the high-precision multireflection time-of-flight technique. The radioisotopes have been produced at RIKEN's Radioactive Isotope Beam Factory (RIBF) and delivered to the novel designed gas cell and multireflection system, which has been recently commissioned downstream of the ZeroDegree spectrometer following the BigRIPS separator. For Ti and V, the mass uncertainties have been reduced down to the order of 10 keV, shedding new light on the shell effect in Ti and V isotopes by the first high-precision mass measurements of the critical species Ti and V. With the new precision achieved, we reveal the nonexistence of the empirical two-neutron shell gaps for Ti and V, and the enhanced energy gap above the occupied p orbit is identified as a feature unique to Ca. We perform new Monte Carlo shell model calculations including the d and g orbits and compare the results with conventional shell model calculations, which exclude the g and the d orbits. The comparison indicates that the shell gap reduction in Ti is related to a partial occupation of the higher orbitals for the outer two valence neutrons at .
Jungclaus, A.*; Grawe, H.*; 西村 俊二*; Doornenbal, P.*; Lorusso, G.*; Simpson, G. S.*; Sderstrm, 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:8 パーセンタイル:54.73(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.
Jungclaus, A.*; Grawe, H.*; 西村 俊二*; Doornenbal, P.*; Lorusso, G.*; Simpson, G. S.*; Sderstrm, 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:18 パーセンタイル:76.95(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.*; Sderstrm, P.-A.*; et al.
Physical Review C, 93(4), p.041301_1 - 041301_6, 2016/04
被引用回数:18 パーセンタイル:76.95(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.
Taprogge, J.*; Jungclaus, A.*; Grawe, H.*; 西村 俊二*; Doornenbal, P.*; Lorusso, G.*; Simpson, G. S.*; Sderstrm, 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:24 パーセンタイル:82.23(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.*; Sderstrm, 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:164 パーセンタイル:97.99(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.*; Sderstrm, P.-A.*; et al.
Physics Letters B, 738, p.223 - 227, 2014/11
被引用回数:23 パーセンタイル:79.89(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.*; Sderstrm, 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:68 パーセンタイル:91.89(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*; Sderstrm, 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:25 パーセンタイル:77.50(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.*; Sderstrm, 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:51 パーセンタイル:88.62(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
被引用回数:1 パーセンタイル:14.38(Physics, Nuclear)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。
森川 恒安*; 郷農 靖之*; 森田 浩介*; 岸田 隆*; 村上 健*; 井出口 栄治*; 熊谷 秀和*; G.H.Liu*; A.Ferragut*; 吉田 敦*; et al.
Physics Letters B, 350, p.169 - 172, 1995/00
被引用回数:19 パーセンタイル:70.87(Astronomy & Astrophysics)高スピン核異性体を逆運動学的核融合反応により生成し、不安定核二次ビームとして用いるあたらしい実験手法を開発した。この手法によりHfのK=8核異性体からなる二次ビームをPbの第二次標的に照射し、散乱粒子と脱励起ガンマ線の同時計数法を用いてクーロン励起実験をおこなった。核異性体上に構築されたJ=9の第一励起状態からのガンマ線を測定し、その収量から換算遷移確率B(E;89)の値をもとめた。その結果、この核異性体上の励起状態は基底状態とほぼ同程度の変形をした集団運動の状態であることがわかった。実験データとの比較によると、この核異性体のK量子数はかなり良い量子数であると考えられる。また、この実験は高スピン核異性体二次ビームによる二次反応を用いて行われた初めてのガンマ線核分光実験であった。
A.Ferragut*; 郷農 靖之*; 村上 健*; 森川 恒安*; Y.H.Zhang*; 森田 浩介*; 吉田 敦*; 大島 真澄; 草刈 英栄*; 菅原 昌彦*; et al.
Journal of the Physical Society of Japan, 62(9), p.3343 - 3344, 1993/09
被引用回数:16 パーセンタイル:86.74(Physics, Multidisciplinary)理研リングサイクロトロンからのXeビームを用いてO(Xe,7n)反応によりSmの高スピンアイソマーの探索を行った。核反応生成物は、ガス充填したダイポール磁石・Q磁石から成るイオン輸送系により一次ビームから分離され、プラスチックシンチレーターで止められた。その回りに7台のアンチコンプトンガンマ線分析器を配置した。数10本のガンマ線と粒子の間の同時計数から、励起エネルギー約8.8MeVに0.96+0.19-0.15secの寿命を持つアイソマーの存在が確認された。詳細な崩壊図式の決定はこれからである。