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論文

Electromagnetic properties of low-lying states in neutron-deficient Hg isotopes; Coulomb excitation of $$^{182}$$Hg, $$^{184}$$Hg, $$^{186}$$Hg and $$^{188}$$Hg

Wrzosek-Lipska, K.*; Rezynkina, K.*; Bree, N.*; Zieli$'n$ska, M.*; Gaffney, L. P.*; Petts, A.*; Andreyev, A. N.; Bastin, B.*; Bender, M.*; Blazhev, A.*; et al.

European Physical Journal A, 55(8), p.130_1 - 130_23, 2019/08

https://doi.org/10.1140/epja/i2019-12815-2
 被引用回数：11 パーセンタイル：73.85(Physics, Nuclear)

The neutron-deficient mercury isotopes serve as a classical example of shape coexistence, whereby at low energy near-degenerate nuclear states characterized by different shapes appear. The electromagnetic structure of even-mass $$^{182-188}$$Hg isotopes was studied using safe-energy Coulomb excitation of neutron-deficient mercury beams delivered by the REX-ISOLDE facility at CERN. The population of 0$$^{+}_{1,2}$$, 2$$^{+}_{1,2}$$, and 4$$^{+}_{1}$$ states was observed in all nuclei under study. Reduced $$E2$$ matrix elements coupling populated yrast and non-yrast states were extracted, including their relative signs. These are a sensitive probe of shape coexistence and may be used to validate nuclear models. The experimental results are discussed in terms of mixing of two different configurations and are compared with three different model calculations: the Beyond Mean Field model, the Interacting Boson Model with configuration mixing and the General Bohr Hamiltonian. Partial agreement with experiment was observed, hinting to missing ingredients in the theoretical descriptions.

論文

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

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

https://doi.org/10.1103/PhysRevC.96.054327
 被引用回数：3 パーセンタイル：27.26(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

Uniaxial pressure effect on the magnetic ordered moment and transition temperatures in BaFe$$_{2-x}$$T$$_{x}$$As$$_{2}$$ ($$T$$ = Co,Ni)

Tam, D. M.*; Song, Y.*; Man, H.*; Cheung, S. C.*; Yin, Z.*; Lu, X.*; Wang, W.*; Frandsen, B. A.*; Liu, L.*; Gong, Z.*; et al.

Physical Review B, 95(6), p.060505_1 - 060505_6, 2017/02

https://doi.org/10.1103/PhysRevB.95.060505
 被引用回数：23 パーセンタイル：71.14(Materials Science, Multidisciplinary)

We use neutron diffraction and muon spin relaxation to study the effect of in-plane uniaxial pressure on the antiferromagnetic (AF) orthorhombic phase in BaFe$$_{2-x}$$T$$_{x}$$As$$_{2}$$ and its Co- and Ni-substituted members near optimal superconductivity. In the low-temperature AF ordered state, uniaxial pressure necessary to detwin the orthorhombic crystals also increases the magnetic ordered moment, reaching an 11% increase under 40 MPa for BaFe$$_{1.9}$$Co$$_{0.1}$$As$$_2$$, and a 15% increase for BaFe$$_{1.915}$$Ni$$_{0.085}$$As$$_2$$. We also observe an increase of the AF ordering temperature ($$T_N$$) of about 0.25 K/MPa in all compounds, consistent with density functional theory calculations that reveal better Fermi surface nesting for itinerant electrons under uniaxial pressure. The doping dependence of the magnetic ordered moment is captured by combining dynamical mean field theory with density functional theory, suggesting that the pressure-induced moment increase near optimal superconductivity is closely related to quantum fluctuations and the nearby electronic nematic phase.

論文

Collectivity in the light radon nuclei measured directly via Coulomb excitation

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

https://doi.org/10.1103/PhysRevC.91.064313
 被引用回数：8 パーセンタイル：50.48(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

$$beta$$-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

https://doi.org/10.1103/PhysRevC.88.044321
 被引用回数：38 パーセンタイル：88.74(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

$$alpha$$-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

https://doi.org/10.1103/PhysRevC.87.054311
 被引用回数：16 パーセンタイル：69.99(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

https://doi.org/10.1103/PhysRevLett.105.252502
 被引用回数：189 パーセンタイル：97.23(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$$^{-3}$$ %.

論文

On artificial frequency shifts in infrared spectra obtained from centroid molecular dynamics; Quantum liquid water

Ivanov, S. D.*; Witt, A.*; 志賀 基之; Marx, D.*

Journal of Chemical Physics, 132(3), p.031101_1 - 031101_4, 2010/01

https://doi.org/10.1063/1.3290958
 被引用回数：63 パーセンタイル：89.32(Chemistry, Physical)

セントロイド分子動力学法は経路積分理論から近似的に量子動力学を得る方法の一つである。この論文では、凝集系、特に液体の水において、セントロイド分分子動力学法を用いると、高振動のOHバンドの赤方偏移を過大評価してしまうことを示す。このセントロイド分分子動力学法に特有な振る舞いは、簡単な「調和曲率補正」を用いることで改良することができる。

論文

On the applicability of centroid and ring polymer path integral molecular dynamics for vibrational spectroscopy

Witt, A.*; Ivanov, S. D.*; 志賀 基之; Forbert, H.*; Marx, D.*

Journal of Chemical Physics, 130(19), p.194510_1 - 194510_15, 2009/05

https://doi.org/10.1063/1.3125009
 被引用回数：185 パーセンタイル：98.88(Chemistry, Physical)

セントロイド分子動力学法やリングポリマー分子動力学法は、経路積分分子動力学法を拡張し、複雑な分子系の量子動力学を近似的に解くことのできる手法である。両方法ともに振動分光学に関連した準古典的な時間相関関数、特に赤外スペクトルに関係した双極子自己相関関数などを算出することができる。これらの方法を使い、振動スペクトルの温度依存性や同位体依存性について、簡単な分子を例として系統的に調べる。

論文

Angular tunneling ionization probability of fixed-in-space H$$_{2}$$ molecules in intense laser pulses

Staudte, A.*; Patchkovskii, S.*; Pavi$v{c}$i$'c$, D.*; 赤木 浩; Smirnova, O.*; Zeidler, D.*; Meckel, M.*; Villeneuve, D. M.*; D$"o$rner, R.*; Ivanov, M. Yu.*; et al.

Physical Review Letters, 102(3), p.033004_1 - 033004_4, 2009/01

https://doi.org/10.1103/PhysRevLett.102.033004
 被引用回数：120 パーセンタイル：95.11(Physics, Multidisciplinary)

We propose a new approach to obtain molecular frame photoelectron angular distributions from molecules ionized by intense laser pulses. With our method we study the angular tunnel ionization probability of H$$_{2}$$ at a wavelength of 800 nm over an intensity range of 2-4.5$$times$$10$$^{14}$$ W/cm$$^{2}$$. We find an anisotropy that is stronger than predicted by any existing model. To explain the observed anisotropy and its strong intensity dependence we develop an analytical model in the frame work of the strong field approximation. It expresses molecular ionization as a product of atomic ionization rate and a Fourier transform of the highest occupied molecular orbital filtered by the strong-field ionization process.

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。

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