Andel, B.*; Andreyev, A. N.; Antalic, S.*; Al Monthery, M.*; Barzakh, A.*; Bissell, M. L.*; Chrysalidis, K.*; 他29名*
Physical Review C, 102(1), p.014319_1 - 014319_12, 2020/07
-delayed fission (DF) decay of a low-spin (ls) and a high-spin (hs) isomer in Bi was studied at the ISOLDE facility at CERN. Their DF partial half-lives were determined: , DF(Bi)= 5.6(8) 10 s and , DF(Bi)=1.7(6) 10 s. This work is the first DF study of two states in one isotope and allows the spin dependence of low-energy fission to be explored. The fission fragment mass distribution of a daughter nuclide Pb, following the decay of the high-spin isomer, was deduced and indicates a mixture of symmetric and asymmetric fission modes.
Barzakh, A. E.*; Atanasov, D.*; Andreyev, A. N.; Al Monthery, M.*; Althubiti, N. A.*; Andel, B.*; Antalic, S.*; Blaum, K.*; 他34名*
Physical Review C, 101(6), p.064321_1 - 064321_7, 2020/06
Hyperfine-structure parameters and isotope shift of the isomeric state in Au relative to Au for the 267.6-nm atomic transition have been measured for the first time using the in-source resonance-ionization spectroscopy technique. The magnetic dipole moment and change in the mean-square charge radius for this isomer have been deduced. The observed large isomer shift relative to the ground state in Au confirms the occurrence of the shape coexistence in Au proposed earlier from the analysis of the nuclear spectroscopic data and particle plus triaxial rotor calculations. The analysis of the magnetic moment supports the previously proposed ,  assignment at moderate prolate deformation for Au.
Barzakh, A. E.*; Atanasov, D.*; Andreyev, A. N.; Al Monthery, M.*; Althubiti, N. A.*; Andel, B.*; Antalic, S.*; Blaum, K.*; 他39名*
Physical Review C, 101(3), p.034308_1 - 034308_9, 2020/03
Hyperfine-structure constants for the = 11/2 gold isomers Au have been measured at CERN-ISOLDE, using the in-source laser resonance-ionization spectroscopy technique. From the measured hyperfine constants the differences between hyperfine anomalies have been deduced. These differential hyperfine anomaly values have been used to determine the hyperfine anomaly relative to the stable Au with advanced atomic calculations. Magnetic dipole moments for the gold isomers in question have been deduced, taking into account the corresponding relative hyperfine-anomaly values. It has been shown that the commonly used prescription for the extraction of the magnetic moment values for the gold isotopes should be reconsidered. The magnetic moments calculated by this prescription have been reevaluated by properly accounting for the hyperfine anomaly, which is as large as 10% for several gold isotopes.
Chrysalidis, K.*; Barzakh, A. E.*; Ahmed, R.*; Andreyev, A. N.; Ballof, J.*; Cubiss, J. G.*; Fedorov, D. V.*; Fedosseev, V. N.*; Fraile, L. M.*; Harding, R. D.*; et al.
Nuclear Instruments and Methods in Physics Research B, 463, p.472 - 475, 2020/01
放射壊変によって生成された多数のジスプロシウム同位体について、ISOLDEのレーザー共鳴イオン源(RILIS)を用いてイオン源内レーザー分光法によって研究した。Dyに対する相対的な同位体シフトを (gs) 共鳴遷移を用いて測定した。電子的因子Fとマスシフト因子Mを導出し、それらを使ってDyとDyの平均自乗荷電半径の変化を初めて決定した。
Cubiss, J. G.*; Harding, R. D.*; Andreyev, A. N.; Althubiti, N.*; Andel, B.*; Antalic, S.*; Barzakh, A. E.*; Cocolios, T. E.*; Day Goodacre, T.*; Farooq-Smith, G. J.*; et al.
Physical Review C, 101(1), p.014314_1 - 014314_4, 2020/01
Ghys, L.*; Andreyev, A. N.; Huyse, M.*; Van Duppen, P.*; Antalic, S.*; Barzakh, A.*; Capponi, L.*; Cocolios, T. E.*; Cubiss, J.*; Derkx, X.*; et al.
Physical Review C, 100(5), p.054310_1 - 054310_13, 2019/11
The aim of this work was to investigate the -decay properties of Fr and daughter products. Neutron-deficient francium nuclei are produced at ISOLDE-CERN bombarding a UCx target with 1.4 GeV protons. Due to the very high statistics and the high beam purity, improved decay data for Fr and its daughters were obtained. The observation of crossover transitions positioned the isomeric high-spin level of At at an excitation energy of 265(3) keV. Half-life values of 4.47(5) s and 1.28(10) s were extracted for the ground state and isomeric state of At and 52(3) ms for the ground-state decay of Fr.
Cubiss, J. G.*; Andreyev, A. N.; Barzakh, A. E.*; Andel, B.*; Antalic, S.*; Cocolios, T. E.*; Day Goodacre, T.*; Fedorov, D. V.*; Fedosseev, V. N.*; Ferrer, R.*; et al.
Physical Review C, 99(6), p.064317_1 - 064317_6, 2019/06
Barzakh, A. E.*; Cubiss, J. G.*; Andreyev, A. N.; Seliverstov, M. D.*; Andel, B.*; Antalic, S.*; Ascher, P.*; Atanasov, D.*; Beck, D.*; Biero, J.*; et al.
Physical Review C, 99(5), p.054317_1 - 054317_9, 2019/05
Hyperfine-structure parameters and isotope shifts for the 795-nm atomic transitions in At have been measured at CERN-ISOLDE, using the in-source resonance-ionization spectroscopy technique. Magnetic dipole and electric quadrupole moments, and changes in the nuclear mean-square charge radii, have been deduced. A large inverse odd-even staggering in radii, which may be associated with the presence of octupole collectivity, has been observed. Namely, the radius of the odd-odd isotope At has been found to be larger than the average.
Cubiss, J. G.*; Barzakh, A. E.*; Andreyev, A. N.; 他57名*
Physics Letters B, 786, p.355 - 363, 2018/11
The first accurate measurements of the -decay branching ratio and half-life of the I=1/2 ground state in Tl have been made, along with the first determination of the magnetic moments and I=1/2 spin assignments of the ground states in Au. The results are discussed within the complementary systematics of the reduced -decay widths and nuclear g factors of low-lying, I=1/2states in the neutron-deficient lead region. The findings shed light on the unexpected hindrance of the 1/2 1/2, Tl Au decay, which is explained by a mixing of 3sand 2d configurations in Au, whilst Tl remains a near-pure 3s. This conclusion is inferred from the g factor of Au which has an intermediate value between those of 3s and 2d states. A similar mixed configuration is proposed for the I=1/2 ground state of Au. This mixing may provide evidence for triaxial shapes in the ground states in these nuclei.
Andel, B.*; Andreyev, A.; Antalic, S.*; Barzakh, A.*; Bree, N.*; Cocolios, T. E.*; Comas, V. F.*; Diriken, J.*; Elseviers, J.*; Fedorov, D. V.*; et al.
Physical Review C, 96(5), p.054327_1 - 054327_11, 2017/12
A detailed -decay spectroscopy study of Tl has been performed at ISOLDE (CERN). Z-selective ionization by the Resonance Ionization Laser Ion Source (RILIS) coupled to mass separation provided a high-purity beam of Tl. Fine-structure decays to excited levels in the daughter Au were identified and an -decay scheme of Tl was constructed based on an analysis of - and - - coincidences. Multipolarities of several -ray transitions deexciting levels in Au were determined. Based on the analysis of reduced -decay widths, it was found that all decays are hindered, which signifies a change of configuration between the parent and all daughter states.
Barzakh, A.*; Andreyev, A.; Cocolios, T. E.*; de Groote, R. P.*; Fedorov, D. V.*; Fedosseev, V. N.*; Ferrer, R.*; Fink, D. A.*; Ghys, L.*; Huyse, M.*; et al.
Physical Review C, 95(1), p.014324_1 - 014324_12, 2017/01
Hyperfine structure and isotope shifts have been measured for the ground and isomeric states in the neutron deficient isotopes Tl using the 276.9 nm transition. The experiment has been performed at the CERN Isotope Separator On-Line facility using the in-source resonance-ionization laser spectroscopy technique. Spins for the ground states in Tl have been determined as = 1/2. Magnetic moments and changes in the nuclear mean-square charge radii have been deduced. By applying the additivity relation for magnetic moments of the odd-odd Tl nuclei the leading configuration assignments were confirmed. A deviation of magnetic moments for isomeric states in Tl from the trend of the heavier Tl nuclei is observed. The charge radii of the ground states of the isotopes Tl follow the trend for isotonic (spherical) lead nuclei. The noticeable difference in charge radii for ground and isomeric states of Tl has been observed, suggesting a larger deformation for the intruder-based 9/2 and 10 states compared to the ground states. An unexpected growth of the isomer shift for Tl has been found.
Truesdale, V. L.*; Andreyev, A.; Ghys, L.*; Huyse, M.*; Van Duppen, P.*; Sels, S.*; Andel, B.*; Antalic, S.*; Barzakh, A.*; Capponi, L.*; et al.
Physical Review C, 94(3), p.034308_1 - 034308_11, 2016/09
A nuclear-decay spectroscopy study of the neutron-deficient isotope At is reported where an isotopically pure beam was produced using the selective Resonance Ionization Laser Ion Source and On-Line Isotope Mass Separator (CERN). The fine-structure decay of At allowed the low-energy excited states in the daughter nucleus Bi to be investigated. A -delayed fission study of At was also performed. A mixture of symmetric and asymmetric fission-fragment mass distributions of the daughter isotope Po (populated by decay of At) was deduced based on the measured fission-fragment energies. A DF probability (At) = 9(1)10 was determined.
Van Beveren, C.*; Andreyev, A.; Barzakh, A. E.*; Cocolios, T. E.*; de Groote, R. P.*; Fedorov, D.*; Fedosseev, V. N.*; Ferrer, R.*; Ghys, L.*; Huyse, M.*; et al.
Journal of Physics G; Nuclear and Particle Physics, 43(2), p.025102_1 - 025102_22, 2016/02
-decay spectroscopy of Tl has been performed at the CERN isotope separator on-line (ISOLDE) facility. New fine-structure decays have been observed for both isotopes. -decay branching ratios of 0.089(19), 0.047(6) and 1.22(30) have been deduced for the (10), (7) and (2) states respectively in Tl and a lower limit of 0.49 for the -decay branching ratio of Tl. A new half-life of 9.5(2) s for the (2) state in Tl and 1.9(1) s for the low-spin state in Tl has been deduced. Using - coincidence analysis, multiple rays were observed de-exciting levels in Au fed by Tl decays. The transitions connecting these low-lying states in Au are essential to sort the data and possibly identify bands from inbeam studies in these isotopes. Owing to the complex fine-structure decays and limited knowledge about the structure of the daughter nuclei, only partial level schemes could be constructed for both gold isotopes in the present work. Reduced -decay widths have been calculated and are compared with values obtained in neighboring odd-A and even-A thallium isotopes. Except for the allowed decay of the Tl (10) state, the other fine-structure decays observed in this study are hindered. This points to strong structural changes between parent thallium and daughter gold isotopes.
Van Beveren, C.*; Andreyev, A.; Barzakh, A.*; Cocolios, T. E.*; Fedorov, D.*; Fedosseev, V. N.*; Ferrer, R.*; Huyse, M.*; Kster, U.*; Lane, J. F. W.*; et al.
Physical Review C, 92(1), p.014325_1 - 014325_8, 2015/07
Decay spectroscopy of Tl has been performed at the CERN Isotope Separator On-Line (ISOLDE) facility. An excitation energy of 506.1(1) keV and a half-life of 47.1(7) ms of the intruder based (10) state have been extracted. The internal decay characteristics of this state are determined and discussed, extending the systematics of such states in the even-mass thallium nuclei below neutron midshell at N = 104. The retardation factors of the isomeric M2 and E3 transitions are deduced and compared with retardation factors in neighboring odd-mass and even-mass thallium isotopes. The new information is combined with a review of hindered and unhindered -decay data of Bi populating levels in daughter nuclei Tl and supports the interpretation of the intruder character of the (10) state in Tl.
Fink, D. A.*; Cocolios, T. E.*; Andreyev, A.; Antalic, S.*; Barzakh, A. E.*; Bastin, B.*; Fedorov, D. V.*; Fedosseev, V. N.*; Flanagan, K. T.*; Ghys, L.*; et al.
Physical Review X, 5(1), p.011018_1 - 011018_15, 2015/01
A Laser Ion Source and Trap (LIST) for a thick-target, isotope-separation on-line facility has been implemented at CERN ISOLDE for the production of pure, laser-ionized, radioactive ion beams. The first physics application of the LIST enables the suppression of francium contamination in ion beams of neutron-rich polonium isotopes at ISOLDE by more than 1000 with a reduction in laser-ionization efficiency of only 20. Resonance ionization spectroscopy is performed directly inside the LIST device, allowing the study of the hyperfine structure and isotope shift of Po for the first time. Nuclear decay spectroscopy of Po is performed for the first time, revealing its half-life, -to--decay branching ratio, and -particle energy. This experiment demonstrates the applicability of the LIST at radioactive ion-beam facilities for the production and study of pure beams of exotic isotopes.
Elseviers, J.*; Andreyev, A. N.*; Huyse, M.*; Van Duppen, P.*; Antalic, S.*; Barzakh, A.*; Bree, N.*; Cocolios, T. E.*; Comas, V. F.*; Diriken, J.*; et al.
Physical Review C, 88(4), p.044321_1 - 044321_13, 2013/10
The detailed analysis of the -delayed fission data of Tl is presented. The experiment was performed by producing a pure beam of Tl by means of highly selective resonance laser ionization followed by mass separation with the ISOLDE isotope separator. A surprising asymmetric mass distribution of fission fragments from Hg, the daughter of Tl decays, was obtained. Here, the energy calibration of the silicon detectors, which is crucial for a proper determination of the fission fragments' energy and mass split, is presented and the total kinetic energy and its dependence on the mass split ratio is discussed. A more precise -delayed fission probability of 3.2(2)10 was deduced.
Andreyev, A. N.*; Liberati, V.*; Antalic, S.*; Ackermann, D.*; Barzakh, A.*; Bree, N.*; Cocolios, T. E.*; Diriken, J.*; Elseviers, J.*; Fedorov, D.*; et al.
Physical Review C, 87(5), p.054311_1 - 054311_8, 2013/05
-decay studies of Tl and its dahghter products Au and Ir were carried out in two complementary experiments at the mass separator ISOLDE (CERN) and velocity filter SHIP (GSI). The nucluesu Au has decay properties of half-life 207 ms and -decay energy 6433 keV. The ground state spins and parities for Au and Ir were determined to be 1/2.
Andreyev, A. N.*; Elseviers, J.*; Huyse, M.*; Van Duppen, P.*; Antalic, S.*; Barzakh, A.*; Bree, N.*; Cocolios, T. E.*; Comas, V. F.*; Diriken, J.*; et al.
Physical Review Letters, 105(25), p.252502_1 - 252502_5, 2010/12
A very exotic process of -delayed fission of Tl is studied in detail by using resonant laser ionization with subsequent mass separation at ISOLDE (CERN). In contrast to common expectations, the fission-fragment mass distribution of the post--decay daughter nucleus Hg (/ = 1.25) is asymmetric. This asymmetry is more surprising since a mass-symmetric split of this extremely neutron-deficient nucleus would lead to two Zr fragments, with magic = 50 and semi-magic = 40. This is a new type of asymmetric fission, not caused by large shell effects related to fragment magic proton and neutron numbers, as observed in the actinide region. The newly-measured branching ratio for -delayed fission of Tl is 3.6(7)10 %.
西尾 勝久; Andreyev, A. N.*; Elseviers, J.*; Huyse, M.*; Van Duppen, P.*; Antalic, S.*; Barzakh, A.*; Bree, N.*; Cocolios, T. E.*; Comas, V. F.*; et al.
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