Gerst, R.-B.*; Blazhev, A.*; Moschner, K.*; Doornenbal, P.*; Obertelli, A.*; Orlandi, R.; 他62名*
Physical Review C, 105(2), p.024302_1 - 024302_11, 2022/02
The neutron rich krypton isotopes Kr (=36, =58,59,60 respectively) were investigated at the Radioactive Isotope Beam Facility Facility (RIBF) at RIKEN. The nuclei of interest were produced in nuclear reactions induced by radioactive Kr and Rb beams, prduced via in-flight fission of U, impinging onto the liquid hydrogen target MINOS. The main reactions occurring were (p,pn), (p,p') and (p,2p). The isotopes of interest were separated in the fragment separator BigRIPS, and their rays detected using the DALI2 -ray spectrometer. The Kr provide insights onto the sudden onset of deformation occurring in Zr and Mo isotopes at =60, which is also associated with shape coexistence. In this experiment the level scheme of these isotopes could be extended, and new yrast and non-yrast states were identified. The results were compared with predictions of the "beyond-mean-field" model and the IBM model, and indications of prolate-oblate shape coexistence at =60 in the Kr isotopes was found.
Andel, B.*; Van Duppen, P.*; Andreyev, A. N.; Blazhev, A.*; Grawe, H.*; Lica, R.*; Nadja, H.*; Stryjczyk, M.*; 他52名*
Physical Review C, 104(5), p.054301_1 - 054301_13, 2021/11
A new -decaying state in Bi has been identified at the ISOLDE Decay Station at the CERN-ISOLDE facility. A preferred assignment was suggested for this state based on the -decay feeding pattern to levels in Po and shell-model calculations. The half-life of the state was deduced to be min. The deexcitation of the levels populated in Po by the decay of this state was investigated via coincidences and a number of new levels and transitions were identified. Shell-model calculations for excited states in Bi and Po were performed using two different effective interactions: the H208 and the modified Kuo-Herling particle interaction. Both calculations agree on the interpretation of the new -decaying state as an isomer and allow for the tentative assignment of shell-model states to several high-spin states in Po.
Kleis, H.*; Seidlitz, M.*; Blazhev, A.*; Kaya, L.*; Reiter, P.*; Arnswald, K.*; Dewald, A.*; Droste, M.*; Fransen, C.*; Mller, O.*; et al.
Physical Review C, 104(3), p.034310_1 - 034310_9, 2021/09
ケルン大学のタンデム加速器にて、Ca(B, )Cr反応によってCrの励起状態を生成し、そこから脱励起する励起状態の寿命をドップラーシフト反跳距離法を用いて測定した。状態から状態へ脱励起する遷移の寿命が6.33(46)ps, 状態から状態へ脱励起する励起の寿命が5.61(28)psであることが決定された。その値から, 値を引き出し、これらが殻模型計算の値とよく一致することがわかった。小さな値は、状態と状態が異なる回転バンドに属しているためであると解釈された。
Wrzosek-Lipska, K.*; Rezynkina, K.*; Bree, N.*; Zieliska, M.*; Gaffney, L. P.*; Petts, A.*; Andreyev, A. N.; Bastin, B.*; Bender, M.*; Blazhev, A.*; et al.
European Physical Journal A, 55(8), p.130_1 - 130_23, 2019/08
The neutron-deficient mercury isotopes serve as a classical example of shape coexistence, whereby at low energy near-degenerate nuclear states characterized by different shapes appear. The electromagnetic structure of even-mass Hg isotopes was studied using safe-energy Coulomb excitation of neutron-deficient mercury beams delivered by the REX-ISOLDE facility at CERN. The population of 0, 2, and 4 states was observed in all nuclei under study. Reduced matrix elements coupling populated yrast and non-yrast states were extracted, including their relative signs. These are a sensitive probe of shape coexistence and may be used to validate nuclear models. The experimental results are discussed in terms of mixing of two different configurations and are compared with three different model calculations: the Beyond Mean Field model, the Interacting Boson Model with configuration mixing and the General Bohr Hamiltonian. Partial agreement with experiment was observed, hinting to missing ingredients in the theoretical descriptions.
Kaya, L.*; Vogt, A.*; Reiter, P.*; Siciliano, M.*; 清水 則孝*; 宇都野 穣; Wang, H.-K.*; Gargano, A.*; Coraggio, L.*; Itaco, N.*; et al.
Physical Review C, 100(2), p.024323_1 - 024323_18, 2019/08
Mller-Gatermann, C.*; Dewald, A.*; Fransen, C.*; Auranen, K.*; Badran, H.*; Beckers, M.*; Blazhev, A.*; Braunroth, T.*; Cullen, D. M.*; Fruet, G.*; et al.
Physical Review C, 99(5), p.054325_1 - 054325_7, 2019/05
Flavigny, F.*; Elseviers, J.*; Andreyev, A. N.; Bauer, C.*; Bildstein, V.*; Blazhev, A.*; 他31名*
Physical Review C, 99(5), p.054332_1 - 054332_6, 2019/05
The Ni isotope is known for exhibiting signs of shape coexistence at very low excitation energies. In this work, carried out at REX-Isolde, CERN, the Ni(,) reaction in inverse kinematics was studied for the first time and used to assess directly the active neutrons orbitals responsible its shape coexistence. The main states populated were the ground state, the second state at 1604~keV, and the first excited 2 state at 2033 keV. The analysis of the differential transfer cross-sections and comparison with theoretical DWBA calculations permitted to quantify the contribution of neutron orbits below the =40 gap in the structure of these states. This information is essential to better understand the phenomenon of shape coexistence in the region of medium-heavy nuclei.
Queiser, M.*; Vogt, A.*; Seidlitz, M.*; Reiter, P.*; 富樫 智章*; 清水 則孝*; 宇都野 穣; 大塚 孝治*; 本間 道雄*; Petkov, P.*; et al.
Physical Review C, 96(4), p.044313_1 - 044313_13, 2017/10
Shand, C. M.*; Podolyk, Zs.*; Grska, 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
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.
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
The first -ray spectroscopy of very neutron rich 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 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.
Chen, S.*; Doornenbal, P.*; Obertelli, A.*; Rodriguez, T. R.*; Authelet, G.*; 馬場 秀忠*; Calvet, D.*; Chteau, F.*; Corsi, A.*; Delbart, A.*; et al.
Physical Review C, 95(4), p.041302_1 - 041302_6, 2017/04
Neutron-rich isotopes of selenium, Se, where studied via in beam -ray spectroscopy after nucleon removal reactions at RIBF in RIKEN. The low-energy excitations of these nuclei were investigated using - 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.
Paul, N.*; Corsi, A.*; Obertelli, A.*; Doornenbal, P.*; Authelet, G.*; 馬場 秀忠*; Bally, B.*; Bender, M.*; Calvet, D.*; Chteau, F.*; et al.
Physical Review Letters, 118(3), p.032501_1 - 032501_7, 2017/01
The first measurement of rays emitted by the very neutron rich nuclei Mo (Z=42) and 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 Mo and 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.
Gaffney, L. P.*; Robinson, A. P.*; Jenkins, D. G.*; Andreyev, A. N.; Bender, M.*; Blazhev, A.*; Bree, N.*; Bruyneel, B.*; Butler, P.*; Cocolios, T. E.*; et al.
Physical Review C, 91(6), p.064313_1 - 064313_11, 2015/06
Radioactive ion beams of Rn were studied by means of low-energy Coulomb excitation at REX-ISOLDE, CERN. The electric-quadrupole (E2) matrix elements connecting the first excited 2 to the ground state of these nuclei was extracted, which permits to determine the collectivity of these isotopes, which in both cases is deduced to be weak, as expected from the low-lying level-energy scheme. Comparisons were also made with beyond-mean-field model calculations and the magnitude of the transitional quadrupole moments are well reproduced.
Diriken, J.*; Patronis, N.*; Andreyev, A. N.; Antalic, S.*; Bildstein, V.*; Blazhev, A.*; Darby, I. G.*; De Witte, H.*; Eberth, J.*; Elseviers, J.*; et al.
Physical Review C, 91(5), p.054321_1 - 054321_15, 2015/05
Excited states up to an excitation energy of 5.8 MeV were populated in the neutron-rich isotope Ni via the Ni(d,p) transfer reaction at REX-Isolde, CERN. In particular, single-neutron states above the N=40 sub-shell gap were populated, and the relative spectroscopic factors were extracted using distorted-wave Born approximation analysis. The positive parity g, d and s neutron orbits above the shell closure are assumed to induce strong quadrupole collectivity in neutron-rich Fe and Cr isotopes. The extracted relative spectroscopic factors show that the strength of the d orbit is mostly split over two states, hinting to substantial mixing of the neutron d configuration with collective modes of the core. The size of the N=50 shell gap was also estimated, and found to be 2.6 MeV near Ni, as also determined in lighter Ni isotopes.
Diriken, J.*; Patronis, N.*; Andreyev, A. N.*; Antalic, S.*; Bildstein, V.*; Blazhev, A.*; Darby, I. G.*; De Witte, H.*; Eberth, J.*; Elseviers, J.*; et al.
Physics Letters B, 736, p.533 - 538, 2014/09
The neutron orbits , d and s are assumed to be responsible for the swift onset of collectivity observed in the region below Ni. In order to gather information on the single-particle energies and spectroscopic factors of these orbitals, single-particle states in the nucleus Ni were populated using the reaction Ni(d,p), in inverse kinematics, at REX-ISOLDE, CERN. The new isotope was studied using combined particle- spectroscopy. Comparison with DWBA calculations, permitted the identification of positive parity states with a substantial amount of d (1007 keV) and d (2207 and 3277 keV) single-particle strength. Comparisons with extended Shell-Model calculations was also performed to confirm the single-particle nature of these states, and to deduce general properties around Ni.
Illana, A.*; Jungclaus, A.*; Orlandi, R.; Perea, A.*; Bauer, C.*; Briz, J. A.*; Egido, J. L.*; Gernhuser, R.*; Leske, J.*; Mcher, D.*; et al.
Physical Review C, 89(5), p.054316_1 - 054316_11, 2014/05
The factor of the first excited state in Zn was measured using the transient-field technique in combination with Coulomb excitation. The experiment was ran at REX-ISOLDE, CERN, and the -ray perturbed angular correlations were measured using 4 triple Germanium clusters of the Miniball array. The experimental result (2) = +0.47(14) is significant to establish the structure of the Zn isotopes near N=40. Comparison with shell-model calculations reveal that to reproduce the measured energies and B(E2) of the Zn isotopes around N=40, both the proton excitations from the orbit and neutron excitations into the and orbits are essential. Furthermore, beyond-mean-field calculations reveal the need to include the triaxial degree of freedom.
Podolyk, Zs.*; Steer, S. J.*; Pietri, S.*; Werner-Malento, E.*; Regan, P. H.*; Rudolph, D.*; Garnsworthy, A. B.*; Hoischen, R.*; Grska, M.*; Gerl, J.*; et al.
European Physical Journal; Special Topics, 150(1), p.165 - 168, 2007/11
Pbの核破砕反応を用いて多数の特殊な原子核を生成した。アイソマー崩壊の後に遅延線を測定し、励起状態の核構造研究を行った。その結果、中性子数126を持つ中性子過剰核Ptの励起状態について初めての実験的な情報を得ることができた。また、既に報告されているTb and Gdの and アイソマーからの崩壊線を観測した。これらのアイソマーは、核破砕反応で生成した最も高いdiscreteな励起状態であり、本手法を用いることにより、高スピン核構造研究の新たな展開が可能になると考えられる。
Pietri, S.*; Regan, P. H.*; Podolyk, Zs.*; Rudolph, D.*; Steer, S. J.*; Garnsworthy, A. B.*; Werner-Malento, E.*; Hoischen, R.*; Grska, M.*; Gerl, J.*; et al.
Nuclear Instruments and Methods in Physics Research B, 261(1-2), p.1079 - 1083, 2007/08
Regan, P. H.*; Garnsworthy, A. B.*; Pietri, S.*; Caceres, L.*; Grska, M.*; Rudolph, D.*; Podolyk, Zs.*; Steer, S. J.*; Hoischen, R.*; Gerl, J.*; et al.
Nuclear Physics A, 787(1), p.491c - 498c, 2007/05