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論文

Detailed $$alpha$$-decay study of $$^{180}$$Tl

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

 パーセンタイル:100(Physics, Nuclear)

A detailed $$alpha$$-decay spectroscopy study of $$^{180}$$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 $$^{180}$$Tl. Fine-structure $$alpha$$ decays to excited levels in the daughter $$^{176}$$Au were identified and an $$alpha$$-decay scheme of $$^{180}$$Tl was constructed based on an analysis of $$alpha$$-$$gamma$$ and $$alpha$$-$$gamma$$ -$$gamma$$ coincidences. Multipolarities of several $$gamma$$-ray transitions deexciting levels in $$^{176}$$Au were determined. Based on the analysis of reduced $$alpha$$-decay widths, it was found that all $$alpha$$ decays are hindered, which signifies a change of configuration between the parent and all daughter states.

論文

Changes in mean-squared charge radii and magnetic moments of $$^{179-184}$$Tl measured by in-source laser spectroscopy

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

 被引用回数:10 パーセンタイル:8.11(Physics, Nuclear)

Hyperfine structure and isotope shifts have been measured for the ground and isomeric states in the neutron deficient isotopes $$^{179-184}$$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 $$^{179,181,183}$$Tl have been determined as $$I$$ = 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 $$^{182,184}$$Tl from the trend of the heavier Tl nuclei is observed. The charge radii of the ground states of the isotopes $$^{179-184}$$Tl follow the trend for isotonic (spherical) lead nuclei. The noticeable difference in charge radii for ground and isomeric states of $$^{183,184}$$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 $$^{183}$$Tl has been found.

論文

$$beta$$-delayed fission and $$alpha$$ decay of $$^{196}$$At

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

 被引用回数:5 パーセンタイル:36.63(Physics, Nuclear)

A nuclear-decay spectroscopy study of the neutron-deficient isotope $$^{196}$$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 $$alpha$$ decay of $$^{196}$$At allowed the low-energy excited states in the daughter nucleus $$^{192}$$Bi to be investigated. A $$beta$$-delayed fission study of $$^{196}$$At was also performed. A mixture of symmetric and asymmetric fission-fragment mass distributions of the daughter isotope $$^{196}$$Po (populated by $$beta$$ decay of $$^{196}$$At) was deduced based on the measured fission-fragment energies. A $$beta$$DF probability $$P_{rm beta DF}$$($$^{196}$$At) = 9(1)$$times$$10$$^{-5}$$ was determined.

論文

$$alpha$$-decay study of $$^{182,184}$$Tl

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

 被引用回数:5 パーセンタイル:36.63(Physics, Nuclear)

$$alpha$$-decay spectroscopy of $$^{182,184}$$Tl has been performed at the CERN isotope separator on-line (ISOLDE) facility. New fine-structure $$alpha$$ decays have been observed for both isotopes. $$alpha$$-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 $$^{184}$$Tl and a lower limit of 0.49$$%$$ for the $$alpha$$-decay branching ratio of $$^{182}$$Tl. A new half-life of 9.5(2) s for the (2$$^{-}$$) state in $$^{184}$$Tl and 1.9(1) s for the low-spin state in $$^{182}$$Tl has been deduced. Using $$alpha$$-$$gamma$$ coincidence analysis, multiple $$gamma$$ rays were observed de-exciting levels in $$^{178,180}$$Au fed by $$^{182,184}$$Tl $$alpha$$ decays. The $$gamma$$ transitions connecting these low-lying states in $$^{178,180}$$Au are essential to sort the data and possibly identify bands from inbeam studies in these isotopes. Owing to the complex fine-structure $$alpha$$ 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 $$alpha$$-decay widths have been calculated and are compared with values obtained in neighboring odd-A and even-A thallium isotopes. Except for the allowed $$alpha$$ decay of the $$^{184}$$Tl (10$$^{-}$$) state, the other fine-structure $$alpha$$ decays observed in this study are hindered. This points to strong structural changes between parent thallium and daughter gold isotopes.

論文

Internal decay of the (10$$^{-}$$) intruder state in $$^{184}$$Tl

Van Beveren, C.*; Andreyev, A.; Barzakh, A.*; Cocolios, T. E.*; Fedorov, D.*; Fedosseev, V. N.*; Ferrer, R.*; Huyse, M.*; K$"o$ster, U.*; Lane, J. F. W.*; et al.

Physical Review C, 92(1), p.014325_1 - 014325_8, 2015/07

 被引用回数:6 パーセンタイル:39.07(Physics, Nuclear)

Decay spectroscopy of $$^{184}$$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 $$alpha$$-decay data of $$^{187-192}$$Bi populating levels in daughter nuclei $$^{183-188}$$Tl and supports the interpretation of the intruder character of the (10$$^{-}$$) state in $$^{184}$$Tl.

論文

Collectivity in the light radon nuclei measured directly via Coulomb excitation

Gaffney, L. P.*; Robinson, A. P.*; Jenkins, D. G.*; Andreyev, A.; 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

 被引用回数:7 パーセンタイル:34.06(Physics, Nuclear)

Radioactive ion beams of $$^{202,204}$$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.

論文

In-source laser spectroscopy with the laser ion source and trap; First direct study of the ground-state properties of $$^{217,219}$$Po

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

 被引用回数:12 パーセンタイル:22.29(Physics, Multidisciplinary)

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 $$^{217}$$Po for the first time. Nuclear decay spectroscopy of $$^{219}$$Po is performed for the first time, revealing its half-life, $$alpha$$-to-$$beta$$-decay branching ratio, and $$alpha$$-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.

論文

Single-neutron orbits near $$^{78}$$Ni; Spectroscopy of the N=49 isotope $$^{79}$$Zn

Orlandi, R.; M$"u$cher, D.*; Raabe, R.*; Jungclaus, A.*; Pain, S. D.*; Bildstein, V.*; Chapman, R.*; de Angelis, G.*; Johansen, J. G.*; Van Duppen, P.*; et al.

Physics Letters B, 740, p.298 - 302, 2015/01

 被引用回数:15 パーセンタイル:13.65(Astronomy & Astrophysics)

Single-neutron states in $$^{79}$$Zn have been populated using the reaction $$^{78}$$Zn(d,p) at REX-Isolde, CERN. The analysis reveals that the lowest excited states in $$^{79}$$Zn lie at approximately 1 MeV, and involve neutron orbits above the N=50 shell gap. A 5/2$$^{+}$$ configuration was assigned to the 983-keV state. Comparison with large-scale shell model calculations supports a robust neutron N=50 shell closure for $$^{78}$$Ni. These data constitute an important step towards the understanding the magicity of $$^{78}$$Ni and the structure of nuclei in the region.

論文

$$beta$$-delayed fission of $$^{180}$$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

 被引用回数:26 パーセンタイル:9.87(Physics, Nuclear)

The detailed analysis of the $$beta$$-delayed fission data of $$^{180}$$Tl is presented. The experiment was performed by producing a pure beam of $$^{180}$$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 $$^{180}$$Hg, the daughter of $$^{180}$$Tl $$beta$$ 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 $$beta$$-delayed fission probability of 3.2(2)$$times$$10$$^{-3}$$$$%$$ was deduced.

論文

Measurement of the first ionization potential of astatine by laser ionization spectroscopy

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

 被引用回数:50 パーセンタイル:5.27(Multidisciplinary Sciences)

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.

論文

$$alpha$$-decay spectroscopy of the chain $$^{179}$$Tl$$^{g}$$ $$rightarrow$$ $$^{175}$$Au$$^{g}$$ $$rightarrow$$ $$^{171}$$Ir$$^{g}$$ $$rightarrow$$ $$^{167}$$Re$$^{m}$$

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

 被引用回数:13 パーセンタイル:27.16(Physics, Nuclear)

$$alpha$$-decay studies of $$^{179}$$Tl$$^{g}$$ and its dahghter products $$^{175}$$Au$$^{g}$$ and $$^{171}$$Ir$$^{g}$$ were carried out in two complementary experiments at the mass separator ISOLDE (CERN) and velocity filter SHIP (GSI). The nucluesu $$^{175}$$Au$$^{g}$$ has $$alpha$$ decay properties of half-life 207 ms and $$alpha$$-decay energy 6433 keV. The ground state spins and parities for $$^{175}$$Au and $$^{171}$$Ir were determined to be 1/2$$^{+}$$.

論文

New type of asymmetric fission in proton-rich nuclei

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

 被引用回数:120 パーセンタイル:3.19(Physics, Multidisciplinary)

A very exotic process of $$beta$$-delayed fission of $$^{180}$$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-$$beta$$-decay daughter nucleus $$^{180}$$Hg ($$N$$/$$Z$$ = 1.25) is asymmetric. This asymmetry is more surprising since a mass-symmetric split of this extremely neutron-deficient nucleus would lead to two $$^{90}$$Zr fragments, with magic $$N$$ = 50 and semi-magic $$Z$$ = 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 $$beta$$-delayed fission of $$^{180}$$Tl is 3.6(7)$$times$$10$$^{-3}$$ %.

口頭

Nuclear moments of the radioactive isotope $$^{131}$$La determined by collinear fast-beam laser spectroscopy

飯村 秀紀; Schuessler, H. A.*; Buchinger, F.*; Cocolios, T.*; Crawford, J. E.*; Gulick, S.*; Lee, J. K. P.*; Levy, C. D. P.*; Pearson, M.*; Lioubimov, V.*; et al.

no journal, , 

希土類元素では、中性子数が74近傍で原子核の変形度が急激に大きくなることが核構造模型から予測されている。この領域を調べるために、$$^{131}$$La(N=74)の超微細構造を初めて測定した。これは、われわれがこれまで行ってきた$$^{135,137-139}$$Laのオフライン・レーザー分光実験をオンライン実験に発展させたものである。放射性核種である$$^{131}$$La(T$$_{1/2}$$=59min)は、TRIUMFサイクロトロンの陽子ビームを用いて核破砕反応により生成した。超微細構造スペクトルは、コリニア・レーザービーム分光の手法により観測した。得られた超微細構造定数より$$^{131}$$Laの原子核の電磁気モーメントを決定した。また、particle triaxial-rotor模型をもとに、モーメントの理論値を計算した。両者を比較した結果、$$^{131}$$Laの原子核が大きく非軸対称変形しいると仮定すると、理論値は実験値を再現することがわかった。

口頭

陽子過剰原子核の核分裂

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.

no journal, , 

陽子過剰な原子核$$^{180}$$Hgの低励起エネルギー核分裂を測定した。CERN-ISOLDEにおいて$$^{180}$$Tlをアイソトープ分離し、このベータ崩壊によって娘核$$^{180}$$Hgを励起さることで、この核分裂を観測した(ベータ崩壊遅延核分裂)。核分裂特性を調べたところ、中性子数50の閉殻を有する$$^{90}$$Zr原子核は生成されず、質量数80と100に収率の最大を有する非対称な核分裂を示した。また、原子力機構タンデム加速器において、陽子過剰原子核のインビーム核分裂実験を行った。この結果、ウランなど従来の核分裂と異なり、励起エネルギーが増加しても質量非対称度が変化しないことがわかった。

口頭

Laser spectroscopy of the neutron deficient La isotopes

飯村 秀紀; Buchinger, F.*; Crawford, J. E.*; Gulick, S.*; Cocolios, T. E.*; Kolomenski, A.*; Fahes, M.*; Schuessler, H. A.*

no journal, , 

$$^{131}$$La(T$$_{1/2}$$=59m)の磁気モーメントと四重極モーメントをコリニア・レーザー分光の手法で測定した。実験はTRIUMF(カナダ)のISAC施設で行った。中性子欠損La同位体については、原子核の非軸対称変形がTotal Routhian Surfaces計算などにより理論的に予測されている。これを検証するために、非軸対称変形を含んだ計算を行い、実験と比較した。計算は、TRSで予測されている変形度から、Particle Triaxial Rotor Modelによりモーメントを計算した。その結果、変形度に特に敏感な四重極モーメントについて理論と実験の良い一致が得られた。一方、非軸対称変形を含まない計算では実験値を再現できず、TRS計算などの予測通り、$$^{131}$$Laが非軸対称変形していることが検証された。同様の計算を、JAEAタンデム加速器で以前に測定した$$^{135}$$Laのモーメントについても行い、この原子核も非軸対称変形していることを確認した。

口頭

Low-energy states in $$^{79}$$Zn and the structure of $$^{78}$$Ni

Orlandi, R.; M$"u$cher, D.*; Raabe, R.*; Jungclaus, A.*; Pain, S. D.*; Bildstein, V.*; Chapman, R.*; de Angelis, G.*; Johansen, J. G.*; Van Duppen, P.*; et al.

no journal, , 

Single-neutron states in the $$N$$ = 49 isotope $$^{79}$$Zn were populated in the $$^{78}$$Zn(d,p)$$^{79}$$Zn transfer reaction at REX-ISOLDE, CERN. The combined detection of protons ejected in the reaction and of $$gamma$$ rays emitted by $$^{79}$$Zn permitted the identification of the lowest-lying 5/2$$^+$$ and 1/2$$^+$$ excited states. The analysis of proton angular distributions links these states to a significant amount of single-particle strength around 1 MeV, and specifically to the $$nu$$d$$_{5/2}$$ and $$nu$$s$$_{1/2}$$ neutron orbits, which lie above the $$N$$ = 50 neutron shell gap. Comparison with large-scale-shell-model calculations supports a robust $$N$$ = 50 shell-closure for $$^{78}$$Ni. These data constitute a considerable step towards the understanding of the magicity of $$^{78}$$Ni and of the structure of isotopes in the region.

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