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Heideman, J.*; Grzywacz, R.*; Xu, Z. Y.*; Madurga, M.*; Escher, J. E.*; 河野 俊彦*; Algora, A.*; Andreyev, A. N.; 他41名*
Physical Review C, 108(2), p.024311_1 - 024311_9, 2023/08
被引用回数:1 パーセンタイル:40.52(Physics, Nuclear)-delayed neutron emission was observed in the study of the decay of In at ISOLDE CERN. Neutron emission probabilities from the unbound states in Sn to known low-lying, single-particle states in Sn were measured. The neutron energies were determined using the time-of-flight technique and the decay from excited states in Sn was studied by detecting its rays. Individual -delayed neutron emission probabilities were determined by correlating the relative intensities and energies of neutrons and rays. The new results suggest the violation of the assumption that neutrons are emitted statistically via the intermediate compound nucleus. This impacts the neutron-emission probabilities and other properties of nuclei participating in the r-process. A model of neutron emission, which links the observed neutron emission probabilities to nuclear shell effects, is proposed.
Xu, Z. Y.*; Madurga, M.*; Grzywacz, R.*; King, T. T.*; Algora, A.*; Andreyev, A. N.; 他43名*
Physical Review C, 108(1), p.014314_1 - 014314_9, 2023/07
被引用回数:7 パーセンタイル:87.68(Physics, Nuclear)Nuclei in the vicinity of doubly magic nuclei away from the line of stability provide a tremendous testing ground to study the evolution of nuclear shell structure as a function of the unbalance between proton and neutron numbers. The decay In (Z=49, N=83), just one proton below and one neutron above doubly magic Sn, were studied at the ISOLDE Decay Station. Using the RILIS laser ion source, separate measurements of the 9/2 ground state and 1/2 isomer were carried out. With the use of -delayed neutron and -ray spectroscopy, the decay strengths above the neutron separation energy were quantified for the first time. The spins and parities to the neutron-unbound states based were assigned based on the -decay selection rules, the log ft values, and systematics. The experimental findings greatly extend the current knowledge of the In decay from previous works, providing the -strength distribution southeast of Sn.
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
被引用回数:3 パーセンタイル:52.30(Physics, Nuclear)The nuclear structure of Cf produced by the O+Cf multinucleon transfer reaction was investigated using -ray spectroscopy. Analysis of the -ray spectrum of 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".
Huang, H.*; Zhang, W. Q.*; Andreyev, A. N.; Liu, Z.*; Seweryniak, D.*; Li, Z. H.*; Guo, C. Y.*; Barzakh, A. E.*; Van Duppen, P.*; Andel, B.*; et al.
Physics Letters B, 833, p.137345_1 - 137345_8, 2022/10
被引用回数:1 パーセンタイル:22.33(Astronomy & Astrophysics)The decay of the 13/2 isomeric state in Hg was observed for the first time following the decay of the 13/2 isomer in Pb produced in the NdCr reaction. Using - delayed coincidence measurements, the half-life of this isomer was measured to be 290(30) s. This isomer is proposed to deexcite by an unobserved low-energy 2 transition to the known 9/2 member of a strongly prolate-deformed 7/2[514] band, followed by a 105-keV 1 transition to the bandhead. A lower limit of B(2)0.018 W.u. was deduced for the unobserved transition. The presumed retardation is proposed to be due to the notable shape change between the initial, nearly spherical, and the final, strongly deformed, states. A similar scenario is also considered for the 13/2 isomer in Hg, suggesting both are cases of shape isomers. The B(2) systematics of neutron transitions across the nuclear chart is discussed.
Zhang, M. M.*; Tian, Y. L.*; Wang, Y. S.*; Zhang, Z. Y.*; Gan, Z. G.*; Yang, H. B.*; Huang, M. H.*; Ma, L.*; Yang, C. L.*; Wang, J. G.*; et al.
Physical Review C, 106(2), p.024305_1 - 024305_6, 2022/08
被引用回数:3 パーセンタイル:52.30(Physics, Nuclear)The extremely neutron-deficient even-even uranium isotopes U were produced in the complete-fusion reactions induced by impinging Ar and Ca ions on W targets. Fusion evaporation residues were separated in flight by the gas-filled recoil separator SHANS (Spectrometer for Heavy Atoms and Nuclear Structure) and subsequently identified using the recoil--correlation method. In this paper, we report on new -decay activities with keV for U and keV for U, which decay from the 8 isomeric states of U into the 2 states of their daughter nuclei Th, respectively. The new results extend the systematics of the -decay fine structure for the = 124 and 126 even-even isotones.
Zhang, W. Q.*; Andreyev, A. N.; Liu, Z.*; Seweryniak, D.*; Huang, H.*; 他37名*
Physical Review C, 106(2), p.024317_1 - 024317_11, 2022/08
被引用回数:4 パーセンタイル:62.14(Physics, Nuclear)The neutron-deficient Bi and Po isotopes have been studied by -ray spectroscopy using the recoil-decay tagging technique with the Argonne Gas-Filled Analyzer. A new 0.25(5)-micro second isomeric state and a prompt cascade formed by 319-, 366-, and 462-keV rays have been established on top of the (10) -decaying isomer in Bi. The first excited (2) state in Po was identified, its excitation energy of 242(2) keV continues the nearly constant trend for the first 2 states in Po. The state is most likely a member of a prolate rotational band built on the ground state, albeit mixing with other coexisting configurations cannot be excluded. The new results obtained in the present work provide new information to shape coexistence in bismuth and polonium isotopes near the neutron midshell at = 104. In this mass region, a reduction in the prompt -ray yield obtained with recoil decay tagging was observed for a few nuclides, and the possible reasons are presented.
Zhang, W. Q.*; Andreyev, A. N.; Liu, Z.*; Seweryniak, D.*; Huang, H.*; Li, Z. H.*; Li, J. G.*; Guo, C. Y.*; 他34名*
Physics Letters B, 829, p.137129_1 - 137129_7, 2022/06
被引用回数:6 パーセンタイル:76.40(Astronomy & Astrophysics)Prompt and delayed -ray spectroscopy of the neutron-deficient, semi-magic isotope Pb has been performed at the Argonne Gas-Filled Analyzer. A new 5.15(15)-s isomeric state at only 308 keV above the spherical 3/2 ground state is identified and classified as a shape isomer. A strongly-coupled band is observed on top of the isomer, which is nearly identical to the one built on the prolate 7/2[514] Nilsson state in the isotone Hg. Based on this similarity and on the result of the potential-energy surface calculations, the new isomer in Pb is proposed to originate from the same configuration. The retarded character of the 308-keV transition can be well explained by the significant difference between the prolate parent and spherical daughter configurations, leading to the shape isomerism. The combined results of the present work and the previous -decay and laser spectroscopy studies present evidence for triple shape coexistence at low energy in the negative-parity configurations of Pb, which is well reproduced by the potential-energy surface calculations.
Venhart, M.*; Andreyev, A. N.; Cubiss, J. G.*; Wood, J. L.*; Barzakh, A. E.*; Van Beveren, C.*; Cocolios, T. E.*; de Groote, R. P.*; 他19名*
Physical Review C, 105(3), p.034338_1 - 034338_9, 2022/03
被引用回数:2 パーセンタイル:52.30(Physics, Nuclear)The neutron-deficient region of isotopes around =82 is the best studied example of low-energy shape coexistence in nuclei. In this work, the internal transition decay and decay of the 53.3-ms isomeric state in Tl were studied at ISOLDE, CERN. The branching for the internal decay was measured to be 98.5(4)%, while the much weaker decay branching is only about 1.4(4)%. The new results include the first identification of an transition feeding the 3/2 excited state in Tl. Three decays from the Tl isomer were also oserved, and revealed the population of a candidate 9/2 state in Au which has been linked to shape coexistence in the Au nuclei. It is expected that similarly weak decays from isomeric states may be found also in neighbouring Tl isotopes.
Barzakh, A. E.*; Andreyev, A. N.; Atanasov, D.*; Cubiss, J. G.*; Harding, R. D.*; Al Monthery, M.*; Althubiti, N. A.*; Andel, B.*; 他38名*
Nuclear Instruments and Methods in Physics Research B, 513, p.26 - 32, 2022/02
被引用回数:1 パーセンタイル:22.33(Instruments & Instrumentation)The yield of 18 beams of radioactive gold nuclei produced by irradiating the ISOLDE uranium target with 1.4-GeV protons was measured. The production-efficiency dependence on the half-life was derived using the in-target production calculations. Three release models were tested to describe the results. Irregularities in the efficiency curve for 3 long-lived high-spin gold isomers (Au) were found, which require further investigation.
Kozulin, E. M.*; Knyazheva, G. N.*; Itkis, I. M.*; Itkis, M. G.*; Mukhamejanov, Y. S.*; Bogachev, A. A.*; Novikov, K. V.*; Kirakosyan, V. V.*; Kumar, D.*; Banerjee, T.*; et al.
Physical Review C, 105(1), p.014607_1 - 014607_12, 2022/01
被引用回数:18 パーセンタイル:95.49(Physics, Nuclear)Asymmetric fission in the neutron-deficient Hg region was first observed about 10 years ago at ISOLDE, and caused a revision of the current understanding of fission in this region. In this work, the fission of Hg and Pd were studied using the time-of-flight spectrometer CORSET at the Flerov Laboratory in Dubna. The observed fission fragments mass distributions of the different isotopes suggest the presence of four concurrent fission modes, one symmetric and three asymmetric fission modes. The asymmetric modes differ in the total kinetic energies and fragment mass splits. These results point out the existence of a well deformed proton shell at =36 and a less deformed proton shell at =46.
Day Goodacre, T.*; Afanasjev, A. V.*; Barzakh, A. E.*; Nies, L.*; Marsh, B. A.*; Sels, S.*; Perera, U. C.*; Ring, P.*; Wienholz, F.*; Andreyev, A. N.; et al.
Physical Review C, 104(5), p.054322_1 - 054322_18, 2021/11
被引用回数:16 パーセンタイル:89.06(Physics, Nuclear)Combining laser spectroscopy with Penning-trap mass spectroscopy at the Isolde facility at CERN, the charge radii of neutron-rich mercury isotopes Hg were successfully measured. Furthermore, more precise values for the masses of Hg was obtained, as well as the magnetic moment of Hg. These results were used to understand the systematics of Hg isotopes across the =126 shell closure. Comparison with covariant density functional theory calculations revealed that in particular the 1 and 2 neutron orbitals affect the evolution of charge radii.
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
被引用回数:5 パーセンタイル:40.24(Physics, Nuclear)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.
Barzakh, A.*; Andreyev, A. N.; Raison, C.*; Cubiss, J. G.*; 他53名*
Physical Review Letters, 127(19), p.192501_1 - 192501_7, 2021/11
被引用回数:34 パーセンタイル:92.22(Physics, Multidisciplinary)The changes in the mean-square charge radius (relative to Bi, magnetic moments and quadrupole moments of the neutron-deficient bismuth isotopes Bi were measured at ISOLDE (CERN). In the experiment, the in-source resonance-ionization spectroscopy technique was employed, which permits to study isotopes produced with rates as low as 0.1/sec. The radii of Bi manifest a large staggering, corresponding to a sudden increase of the radius of Bi relative to its Bi neighbors. This staggering effect occurs at neutron number =105, where shape staggering was also observed in the mercury isotopes. Experimental results were compared with state-of-the-art mean-field calculations, which permit to identify the quasiparticle configurations compatible with the observed spin, parity and magnetic moment of the newly observed states.
Doherty, D. T.*; Andreyev, A. N.; Seweryniak, D.*; Woods, P. J.*; Carpenter, M. P.*; Auranen, K.*; Ayangeakaa, A. D.*; Back, B. B.*; Bottoni, S.*; Canete, L.*; et al.
Physical Review Letters, 127(20), p.202501_1 - 202501_6, 2021/11
被引用回数:10 パーセンタイル:66.31(Physics, Multidisciplinary)Bi is the heaviest known proton emitting isotope. Its decay had been observed, but the assumed ground-state lifetime (s) was incorrect, leading to unexplained hindrance. With two new experiments at Argonne National Laboratory, two states were clearly identified. One is the proton-emitting ground-state (spin 1/2, half-life: 2.8 s), the second is a 58(2) s -decaying isomer. The new data show the inversion of the ground and isomeric states compared to neighboring Bi isotopes. This is the only known example of a ground-state proton decay to a daughter nucleus (Pb) with a major shell closure.
Bogachev, A. A.*; Kozulin, E. M.*; Knyazheva, G. N.*; Itkis, I. M.*; Itkis, M. G.*; Novikov, K. V.*; Kumar, D.*; Banerjee, T.*; Diatlov, I. N.*; Cheralu, M.*; et al.
Physical Review C, 104(2), p.024623_1 - 024623_11, 2021/08
被引用回数:25 パーセンタイル:94.80(Physics, Nuclear)Hg及びPb核の非対称及び対称核分裂モードの研究のため、Ar + Sm,Ca + Sm反応で生成したHg及びPbの質量-エネルギー分布の測定を行った。クーロン障壁エネルギー近傍のエネルギーにおいて、質量-エネルギー分布は二重アーム飛行時間型スペクトロメータCORSETを用いて測定し、以前に測定したPb同位体と比較した。結論として、HgとPb核の非対称核分裂の研究特性はZ36では変形した陽子殻の存在を、Z46では変形しない陽子殻の存在を指摘した。
Harding, R. D.*; Andreyev, A. N.; Barzakh, A. E.*; Cubiss, J. G.*; Van Duppen, P.*; Al Monthery, M.*; Althubiti, N. A.*; Andel, B.*; 他26名*
Physical Review C, 104(2), p.024326_1 - 024326_16, 2021/08
被引用回数:6 パーセンタイル:64.51(Physics, Nuclear)A detailed nuclear spectroscopy study of Au was performed at ISOLDE, CERN. This work provides new insights into the low-lying levels in the daughter nuclei Ir. For Au, the nuclear magnetic moments of a high spin and low spin state were determined and used to predict the most likely configuration of each level. Their -decay branching ratios were also extracted: a 58(5)% branching for the low-spin state, and 29(5)% for the high-spin state.
Brunet, M.*; Podolyk, Zs.*; Berry, T. A.*; Brown, B. A.*; Carroll, R. J.*; Lica, R.*; Sotty, Ch.*; Andreyev, A. N.; Borge, M. J. G.*; Cubiss, J. G.*; et al.
Physical Review C, 103(5), p.054327_1 - 054327_13, 2021/05
被引用回数:7 パーセンタイル:69.46(Physics, Nuclear)The structure of Po populated through the EC/ decay of At is investigated using -ray spectroscopy at the ISOLDE Decay Station. The presented level scheme contains 27 new excited states and 43 new transitions, as well as a further 50 previously observed rays which have been (re)assigned a position. Through the analysis using the shell model calculations approximately half of the -decay strength of At is found to proceed via allowed decay and half via first-forbidden decay. The first-forbidden transitions predominantly populate core excited states at high excitation energies, which is qualitatively understood using shell model considerations.
Gillespie, S. A.*; Stott, A.*; Andreyev, A. N.; 他30名*
Physical Review C, 103(4), p.044307_1 - 044307_9, 2021/04
被引用回数:1 パーセンタイル:15.62(Physics, Nuclear)Proton-rich Au isotopes are an excellent laboratory to study shape coexistence and isomerism at low excitation energies. In this work, two new isomeric states were found in the odd-odd nuclide Au in an experiment at RITU in JYFL, Jyvaskyla. These two isomers significantly extend the current knowledge of this nucleus and pave the way to future in beam studies where they will be used to tag new gamma rays. Possible spin assignments for the new isomeric states are proposed. Finally, the new data will help clarify the poorly known -decay scheme of two long-lived states in the Tl to Au decay chain.
Schmitt, C.*; Lemasson, A.*; Schmidt, K.-H.*; Jhingan, A.*; Biswas, S.*; Kim, Y. H.*; Ramos, D.*; Andreyev, A. N.; Curien, D.*; Ciemala, M.*; et al.
Physical Review Letters, 126(13), p.132502_1 - 132502_6, 2021/04
被引用回数:18 パーセンタイル:82.84(Physics, Multidisciplinary)Isotopic distributions of fragments from fission of the neutron-deficient Hg nuclide are reported. This experimental observable is obtained for the first time in the region around lead using an innovative approach based on inverse kinematics and the coincidence between the large acceptance magnetic spectrometer VAMOS++ and a new detection arm close to the target. The average fragment ratio and prompt neutron multiplicity are derived and compared with current knowledge from actinide fission. A striking consistency emerges, revealing the unexpected dominant role of the proton subsystem with atomic number between the = 28 and 50 magic numbers. The origin of nuclear charge polarization in fission and fragment deformation at scission are discussed.
Zhang, Z. Y.*; Yang, H. B.*; Andreyev, A. N.; Liu, M. L.*; Ma, L.*; 他37名*
Physical Review Letters, 126(15), p.152502_1 - 152502_6, 2021/04
被引用回数:53 パーセンタイル:96.72(Physics, Multidisciplinary)A new -emitting isotope U, produced by the fusion-evaporation reaction W(Ar,4n)U, was identified by employing the gas-filled recoil separator SHANS and the recoil- correlation technique. More precise -decay properties of even-even nuclei U were also measured in the reactions of Ar, Ca beams with W targets. By combining the experimental data, improved -decay reduced widths for the even-even Po-Pu nuclei in the vicinity of the magic neutron number = 126 are deduced. Their systematic trends are discussed in terms of the scheme in order to study the influence of proton-neutron interaction on decay in this region of nuclei. It is strikingly found that the reduced widths of U are significantly enhanced by a factor of two as compared with the systematics for the 84 90 and 126 even-even nuclei. The abnormal enhancement is interpreted by the strong monopole interaction between the valence protons and neutrons occupying the 1 and 1 spin-orbit partner orbits, which is supported by the large-scale shell model calculation.