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Md produced in the 
He + 
Es reaction西尾 勝久; 廣瀬 健太郎; 牧井 宏之; Orlandi, R.; Kean, K. R.*; 塚田 和明; 豊嶋 厚史*; 浅井 雅人; 佐藤 哲也; Chiera, N. M.*; et al.
Physical Review C, 111(4), p.044609_1 - 044609_12, 2025/04
被引用回数：0 パーセンタイル：0.00(Physics, Nuclear)In spontaneous fission (SF) it is found that the mass-asymmetric fission of well-known actinides suddenly changes to the symmetric fission when nucleus has a mass number 
larger than 257. We have measured for the first time fission-fragment mass and total-kinetic-energy (TKE) distributions of the excited compound nucleus Md, populated in the reaction He+Es, using the rare isotope Es with a short half-life, 
=276 days. The fission of Md can be interpreted as involving 3 fission modes: an mass-asymmetric mode and two modes of mass-asymmetric fissions, the latter two are manifested by different TKE values. Predominantly symmetric fission was obtained at the excitation energy of 15.0 MeV. By increasing the energy to 18.0 MeV, the asymmetric fission mode dominates. Both such a strong change of fission modes within a small increase of excitation energy and the enhancement of asymmetric split are new phenomena in fission.
= 82 shell closureZhang, W. Q.*; Andreyev, A. N.; 他10名*
Physical Review C, 110(4), p.044301_1 - 044301_7, 2024/10
被引用回数：0 パーセンタイル：0.00(Physics, Nuclear)Based on the 
values deduced from the linear extrapolations along isotopic chains and on the universal decay law, the proton- and 
-decay partial half-lives are calculated for odd-, even-
neutron-deficient Bi-Pa isotopes. Eight proton-emission states in five new isotopes are suggested. The calculated half-lives for the 1/2
states in 
Bi and 
At are around 100 ns, too short to be studied using the recoil separator setups, which strongly encourages the development of new experimental techniques and devices to search for new submicrosecond proton-emitting nuclei.
Tl; Shape coexistenceGuo, C. Y.*; Andreyev, A. N.; 他38名*
European Physical Journal A, 60(8), p.165_1 - 165_10, 2024/08
被引用回数：0 パーセンタイル：0.00(Physics, Nuclear)The prompt and delayed 
-ray spectra of Tl was studied via the 
Nd(
Cr, 
)Tl fusion-evaporation reaction. The collective bands with one-quasiparticle configurations from the 2
, 1
, 1
, and 1
orbitals and high-lying structures with possible three-quasiparticle configurations are investigated in terms of the tilted axis cranking covariant density functional theory. At low excitation energy, the rotational bands with one-quasiparticle configurations reflect coexistence of three shapes: prolate, triaxial, and oblate. The possible shapes of two microsecond isomers at high excitation energy are proposed.
Bi isotopesHuang, H.*; Andreyev, A. N.; 他37名*
Physical Review C, 110(1), p.014326_1 - 014326_8, 2024/07
被引用回数：2 パーセンタイル：74.11(Physics, Nuclear)The near-symmetric complete fusion reaction 
Kr+
Ag=
Bi
was studied at the gas-filled recoil separator SHANS with an attempt to synthesize the extremely neutron-deficient proton-unbound Bi isotopes. No decay events which could be attributed to them were observed. The two- and three-particle evaporation residues 
Hg (
, 
) and 
Pb(
,
) were identified. Based on the yields of 182,183Pb in the present work and the systematics of the ratios between the cross sections of 
and 
evaporation channels for the most neutron-deficient odd-Z nuclei above lead, the upper limits for the half-lives of Bi were estimated to be less than 0.3
s.
Sn populated in the 
decay of isomerically purified In statesBenito, J.*; Andreyev, A. N.; 他93名*
Physical Review C, 110(1), p.014328_1 - 014328_19, 2024/07
被引用回数：4 パーセンタイル：74.11(Physics, Nuclear)The excited structure of the single-hole nucleus 131Sn populated by the -decay of In was investigated in detail at the ISOLDE facility at CERN. This new experiment took advantage of isomeric purification capabilities provided by resonant ionization, making it possible to independently study the decay of each isomer for the first time. The position of the first-excited 
neutron-hole state was confirmed.
-delayed neutron emitters 
KXu, Z. Y.*; Grzywacz, R.*; Andreyev, A. N.; 他49名*
Physical Review Letters, 133(4), p.042501_1 - 042501_7, 2024/07
被引用回数：2 パーセンタイル：43.84(Physics, Multidisciplinary)We investigated decays of 
K at the ISOLDE Decay Station at CERN in order to understand the mechanism of the -delayed neutron-emission (n) process. The experiment quantified neutron and -ray emission paths for each precursor. We used this information to test the hypothesis, first formulated by Bohr in 1939, that neutrons in the n process originate from the structureless "compound nucleus". The data are consistent with this postulate for most of the observed decay paths. The agreement, however, is surprising because the compound-nucleus stage should not be achieved in the studied decay due to insufficient excitation energy and level densities in the neutron emitter. In the 
K n decay, we found a preferential population of the first excited state in 
Ca that contradicted Bohr's hypothesis. The latter was interpreted as evidence for direct neutron emission sensitive to the structure of the neutron-unbound state. We propose that the observed nonstatistical neutron emission proceeds through the coupling with nearby doorway states that have large neutron-emission probabilities. The appearance of "compound-nucleus" decay is caused by the aggregated small contributions of multiple doorway states at higher excitation energy.
decay of the ground state and of a low-lying isomer in 
BiAndel, B.*; Andreyev, A. N.; 他57名*
Physical Review C, 109(6), p.064321_1 - 064321_18, 2024/06
被引用回数：2 パーセンタイル：74.11(Physics, Nuclear)A detailed -decay study of the low- and high-spin states in Bi has been performed at the ISOLDE Decay Station at the CERN-ISOLDE facility. In total, 48 new levels and 83 new transitions in the -decay daughter Po were identified. Shell-model calculations for excited states in Bi and Po were performed using the H208 and the modified Kuo-Herling particle effective interactions. Based on the experimental observations and the shell-model calculations, the most likely spin and parity assignments for the -decaying states in Bi are (3
) and (8), respectively.
Cubiss, J. G.*; Andreyev, A. N.; 他49名*
Physical Review Letters, 131(20), p.202501_1 - 202501_8, 2023/11
被引用回数：10 パーセンタイル：79.13(Physics, Multidisciplinary)The changes in mean-squared charge radii of neutron-deficient gold nuclei have been determined using the in-source, resonance-ionization laser spectroscopy technique, at the ISOLDE facility (CERN). From these new data, nuclear deformations are inferred, revealing a competition between deformed and spherical configurations. The isotopes 
Au are observed to possess well-deformed ground states and, when moving to lighter masses, a sudden transition to near-spherical shapes is seen in the extremely neutron deficient nuclides, 
Au. A case of shape coexistence and shape staggering is identified in 
Au which has a ground and isomeric state with different deformations. These new data reveal a pattern in ground-state deformation unique to the gold isotopes, whereby, when moving from the heavy to light masses, a plateau of well-deformed isotopes exists around the neutron midshell, flanked by near-spherical shapes in the heavier and lighter isotopes-a trend hitherto unseen elsewhere in the nuclear chart. The experimental charge radii are compared to those from Hartree-Fock-Bogoliubov calculations using the D1M Gogny interaction and configuration mixing between states of different deformation. The calculations are constrained by the known spins, parities, and magnetic moments of the ground states in gold nuclei and show a good agreement with the experimental results.
decay near doubly magic 
SnHeideman, 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：3 パーセンタイル：57.48(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 
-process. A model of neutron emission, which links the observed neutron emission probabilities to nuclear shell effects, is proposed.
-delayed neutron spectroscopy of InXu, 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：9 パーセンタイル：86.72(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.
In; A Rosetta stone for decays of -process nucleiXu, Z. Y.*; Andreyev, A. N.; 他47名*
Physical Review Letters, 131(2), p.022501_1 - 022501_6, 2023/07
被引用回数：4 パーセンタイル：59.55(Physics, Multidisciplinary)The decays from both the ground state and a long-lived isomer of In were studied at the ISOLDE Decay Station (IDS). With a hybrid detection system sensitive to , , and neutron spectroscopy, the comparative partial half-lives (log 
) have been measured for all their dominant -decay channels for the first time, including a low-energy Gamow-Teller transition and several first-forbidden (FF) transitions. Uniquely for such a heavy neutron-rich nucleus, their decays selectively populate only a few isolated neutron unbound states in Sn. Precise energy and branching-ratio measurements of those resonances allow us to benchmark -decay theories at an unprecedented level in this region of the nuclear chart. The results show good agreement with the newly developed large-scale shell model (LSSM) calculations. The experimental findings establish an archetype for the decay of neutron-rich nuclei southeast of Sn and will serve as a guide for future theoretical development aiming to describe accurately the key decays in the rapid-neutron capture (-) process.
isomers in 
CfOrlandi, 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：4 パーセンタイル：52.14(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".
Hg and asymmetric fission of neutron-deficient pre-actinidesJhingan, A.*; Andreyev, A. N.; 他28名*
Physical Review C, 106(4), p.044607_1 - 044607_9, 2022/10
被引用回数：8 パーセンタイル：75.94(Physics, Nuclear)Fission of Hg was induced by fusion of 
Xe and 
Fe. The two fragments were detected in coincidence using VAMOS++ supplemented with a new SEcond Detection arm. For the first time in the pre-actinide region, access to the pre-neutron mass and total kinetic energy distributions, and the simultaneous isotopic identification of one the fission fragment, was achieved. The present work describes the experimental approach, and discusses the pre-neutron observables in the context of an extended asymmetric fission island located southwest of 
Pb. A comparison with different models is performed, demonstrating the importance of this new asymmetric-fission island for elaborating on driving effects in fission.
isomer in Hg and 
(
2) systematics of neutron transitions across the nuclear chartHuang, 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：17.31(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 Nd
Cr
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.
Bi and PoZhang, 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：5 パーセンタイル：52.14(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.
decay of the 8 isomer in 
UZhang, 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：5 パーセンタイル：60.14(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.
PbZhang, 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：65.93(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.
isomeric state in TlVenhart, 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：3 パーセンタイル：43.00(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：2 パーセンタイル：17.31(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.
Hg* and Pt* nuclei at intermediate excitation energiesKozulin, 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：23 パーセンタイル：95.56(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.
