Bronis, A.*; Heberger, F. P.*; Antalic, S.*; Andel, B.*; Ackermann, D.*; Heinz, S.*; Hofmann, S.*; Khuyagbaatar, J.*; Kindler, B.*; Kojouharov, I.*; et al.
Physical Review C, 106(1), p.014602_1 - 014602_12, 2022/07
The decay of excited states in No was investigated by applying the evaporation-residue-conversion-electron correlation technique. Two new isomeric states were observed in No together with the previously known one. Excitation energies of the isomeric states were estimated based on the energies of conversion electrons and rays from correlation chains. These results were in accord with theoretical calculations based on the mean-field models. A tentative decay scheme of isomeric states in No is proposed, and their Nilsson configurations are discussed. The energy decrease of the 11/2 Nilsson level for heavy =153 isotones as a function of increasing proton number is confirmed.
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
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.
Venhart, M.*; Balogh, M.*; Herz, A.*; Wood, J. L.*; Ali, F. A.*; Joss, D. T.*; Andreyev, A. N.; Auranen, K.*; Carroll, R. J.*; Drummond, M. C.*; et al.
Physics Letters B, 806, p.135488_1 - 135488_6, 2020/07
The extremely neutron-deficient isotopes Au were studied by means of in-beam -ray spectroscopy. Specific tagging techniques, -decay tagging in Au and isomer tagging in Au, were used for these studies. Feeding of positive-parity, nearly spherical states, which are associated with 2 and 3 proton-hole configurations, from the 1 proton-intruder configuration was observed in Au. Such a decay path has no precedent in odd-Au isotopes and it is explained by the effect of mixing of wave functions of the initial state.
Gillespie, S. A.*; Andreyev, A. N.; Al Monthery, M.*; Barton, C. J.*; Antalic, S.*; Auranen, K.*; Badran, H.*; Cox, D.*; Cubiss, J. G.*; O'Donnell, D.*; et al.
Physical Review C, 99(6), p.064310_1 - 064310_6, 2019/06
An experiment has been performed to study excited states in the neutron-deficient nucleus Ir via the use of the JUROGAM II high-purity germanium detector array and the RITU gas-filled separator at JYFL, Jyvskyl. By using isomer tagging, an isomeric state with a half-life of 6.58(15) s has been observed in Ir for the first time. It has been established that the isomer decays via a 45.2 () - 26.1 () keV cascade to new states below the previously reported ground state in Ir with . We now reassign this state to the isomeric state discovered in this study.
Andel, B.*; Andreyev, A. N.; 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. N.; 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.
Van Beveren, C.*; Andreyev, A. N.; 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.
西尾 勝久; Andreyev, A. N.*; Chapman, R.*; Derkx, X.*; Dllmann, C. E.*; Ghys, L.*; Heberger, F. P.*; 廣瀬 健太郎; 池添 博*; Khuyagbaatar, J.*; et al.
Physics Letters B, 748, p.89 - 94, 2015/09
Mass distributions of fission fragments from the compound nuclei Hg and Hg formed in fusion reactions Ar+Sm and Ar+Sm, respectively, were measured at initial excitation energies of (Hg)=,3366 MeV and (Hg)=,4871 MeV. In the fission of Hg, the mass spectra were well reproduced by assuming only an asymmetric-mass division, with most probable light and heavy fragment masses /79101. The mass asymmetry for Hg agrees well with that obtained in the low-energy /EC-delayed fission of Tl, from our earlier ISOLDE(CERN) experiment. Fission of Hg is found to proceed in a similar way, delivering the mass asymmetry of /83107, throughout the measured excitation energy range. The persistence as a function of excitation energy of the mass-asymmetric fission for both proton-rich Hg isotopes gives strong evidence for the survival of microscopic effects up to effective excitation energies of compound nuclei as high as 40,MeV. This behavior is different from fission of actinide nuclei and heavier mercury isotope Hg.
Van Beveren, C.*; Andreyev, A. N.; 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.
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.
Rothe, S.*; Andreyev, A. N.*; Antalic, S.*; Borschevsky, A.*; Capponi, L.*; Cocolios, T. E.*; De Witte, H.*; Eliav, E.*; Fedorov, D. V.*; Fedosseev, V. N.*; et al.
Nature Communications (Internet), 4, p.1835_1 - 1835_6, 2013/05
The radioactive element astatine exists only in trace amounts in nature. Its properties can therefore only be explored by study of smallest quantities of artificially produced isotopes or by performing theoretical calculations. One of the most important properties influencing the chemical behaviour is the energy required to remove one electron from the valence shell, referred to as the ionization potential (IP). Here we use laser spectroscopy to probe the optical spectrum of astatine near the ionization threshold. The observed series of Rydberg states allowed the deduction of the IP of the astatine atom for the first time. New ab initio calculations were performed to support the experimental result. The measured value of IP(At) serves as a benchmark for quantum chemistry calculations of the properties of astatine as well as for the theoretical prediction of the ionization potential of super-heavy element 117, the heaviest homologue of astatine.
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.
Rubert, J.*; Dorvaux, O.*; Gall, B. J. P.*; Greenlees, P. T.*; Asfari, Z.*; Piot, J.*; Andersson, L. L.*; 浅井 雅人; Cox, D. M.*; Dechery, F.*; et al.
Journal of Physics; Conference Series, 420, p.012010_1 - 012010_10, 2013/03
Veselsk, M.*; Andreyev, A. N.*; Antalic, S.*; Huyse, M.*; Mller, P.*; 西尾 勝久; Sierk, A. J.*; Van Duppen, P.*; Venhart, M.*
Physical Review C, 86(2), p.024308_1 - 024308_8, 2012/08
The recently measured probabilities of the beta-delayed fission for Tl are used to deduce the fission-barrier heights of the daughter isotopes Hg, undergoing low-energy fission. Four alternative -decay strength functions and four variants of the statistical model of de-excitation of the daughter nucleus are used to determine the fission-barrier height for Hg. Depending on the choice of the model, the deduced fission-barrier heights appear to be between 10 and 40% smaller than theoretical estimates. This observation is verified also for fission-barrier heights extracted using the probability of -delayed fission of Tl. The spread in extracted fission barrier heights results mainly from uncertainties in the magnitude of the pairing gap at the saddle configuration.
Greenlees, P. T.*; Rubert, J.*; Piot, J.*; Gall, B. J. P.*; Andersson, L. L.*; 浅井 雅人; Asfari, Z.*; Cox, D. M.*; Dechery, F.*; Dorvaux, O.*; et al.
Physical Review Letters, 109(1), p.012501_1 - 012501_5, 2012/07
Heberger, F. P.*; Antalic, S.*; Ackermann, D.*; Kalaninov, Z.*; Heinz, S.*; Hofmann, S.*; Streicher, B.*; Kindler, B.*; Kojouharov, I.*; Kuusiniemi, P.*; et al.
European Physical Journal A, 48(5), p.75_1 - 75_9, 2012/05
Nuclear structure and decay of the isotope No and its decay products Fm and Md were investigated by means of - spectroscopy. Besides the established strong transitions from the 9/2 Nilsson level in Fm, populated predominantly by the decay of No, into the ground-state(gs) rotational band, a couple of weaker lines were observed and placed into the Fm level scheme. The transition from the 7/2 level in Es, populated by the decay of Md, into the 9/2 member of the gs rotational band, so far established for other odd-mass Es isotopes, was observed clearly. The GEANT4 simulations were performed to investigate the influence of energy summing between particles and conversion electrons (CE) on the shape of the spectra at different implantation energies, leading to evidence for a weak decay branch of No into the gs of Fm or the ground-state rotational band, respectively.
Antalic, S.*; Heberger, F. P.*; Ackermann, D.*; Heinz, S.*; Hofmann, S.*; Kalaninov, Z.*; Kindler, B.*; Khuyagbaatar, J.*; Kojouharov, I.*; Kuusiniemi, P.*; et al.
European Physical Journal A, 47(5), p.62_1 - 62_12, 2011/05
Nuclear structure and decay of isomer in No were investigated. The isotope was produced by the reaction Ca+Pb. The excitation energy of the known single-particle isomeric state (5/2) was measured by delayed coincidence between -rays and implanted evaporation residues and was placed into the level scheme. In addition, decay of a high-lying multi-quasiparticle isomer in No was studied using e- coincidence measurements. A rotational band populated by its de-excitation was identified in No. A new isomeric state in Fm was observed and a partial-level scheme for this isotope is suggested. In addition transitions from excited levels are reproduced for Md.
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 %.
Heberger, F. P.*; Antalic, S.*; Sulignano, B.*; Ackermann, D.*; Heinz, S.*; Hofmann, S.*; Kindler, B.*; Khuyagbaatar, J.*; Kojouharov, I.*; Kuusiniemi, P.*; et al.
European Physical Journal A, 43(1), p.55 - 66, 2010/01
-rays decay study of two K isomers in No was performed. Two new transitions of 778 and 856 keV could be attributed to the decay pattern of No (T=275 ms). The population of an excited band built up on this isomer (=8) by the decay of No (198 s) could be proven. A spontaneous fission branch of 2.010 was measured for No, and upper limit of 1.210 was estimated for No. These values demonstrate the high stability of multi-quasiparticle configuration against spontaneous fission.
Antalic, S.*; Heberger, F. P.*; Hofmann, S.*; Ackermann, D.*; Heinz, S.*; Kindler, B.*; Kojouharov, I.*; Kuusiniemi, P.*; Leino, M.*; Lommel, B.*; et al.
European Physical Journal A, 38(2), p.219 - 226, 2008/11
The radioactive decay of the isotopes Lr and their daughter products was investigated by means of , prompt and delayed conversion electron coincidence spectroscopy. The experiment was carried out at GSI by using the velocity filter SHIP to separate evaporation residues, produced in the reaction Ca+Bi, from the primary beams. In Lr, a second short-lived isomer with a half-life of 1.91 ms was found. For Lr, new data for transitions of levels in Md populated by decay were observed. The constructed level schemes are useful for the nuclear structure theory.