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論文

Fine structure in the $$alpha$$ decay of $$^{218}$$At

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

 被引用回数:6 パーセンタイル:53.97(Physics, Nuclear)

$$^{218}$$Atの$$alpha$$崩壊について、CERN-ISOLDE施設においてレーザーイオン化法を使うことで研究した。$$alpha$$-$$gamma$$同時計数データを初めて取得し、より精度の良い半減期の値として1.27(6)秒を得た。$$alpha$$崩壊の微細構造を基に新しい$$alpha$$崩壊図式を構築した。それらの結果から、$$^{218}$$Atの基底状態のスピン・パリティは(3$$^{-}$$)がより確からしいことが解ったが、(2)$$^{-}$$の可能性も完全には否定しきれない。

論文

Inverse odd-even staggering in nuclear charge radii and possible octupole collectivity in $$^{217,218,219}$$At revealed by in-source laser spectroscopy

Barzakh, A. E.*; Cubiss, J. G.*; Andreyev, A. N.; Seliverstov, M. D.*; Andel, B.*; Antalic, S.*; Ascher, P.*; Atanasov, D.*; Beck, D.*; Biero$'n$, J.*; et al.

Physical Review C, 99(5), p.054317_1 - 054317_9, 2019/05

 被引用回数:12 パーセンタイル:77.09(Physics, Nuclear)

Hyperfine-structure parameters and isotope shifts for the 795-nm atomic transitions in $$^{217,218,219}$$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 $$^{218}$$At has been found to be larger than the average.

論文

EXILL; A High-efficiency, high-resolution setup for $$gamma$$-spectroscopy at an intense cold neutron beam facility

Jentschel, M.*; Blanc, A.*; de France, G.*; K$"o$ster, U.*; Leoni, S.*; Mutti, P.*; Simpson, G.*; Soldner, T.*; Ur, C.*; Urban, W.*; et al.

Journal of Instrumentation (Internet), 12(11), p.P11003_1 - P11003_33, 2017/11

 被引用回数:38 パーセンタイル:84.92(Instruments & Instrumentation)

A highly efficient array of high-purity germanium (HPGe) detectors was developed and operated at the cold neutron beam facility PF1B of the Institut Laue-Langevin (ILL) to carry out nuclear structure studies, via measurements of $$gamma$$-rays following neutron-induced capture and fission reactions. The setup consisted of a collimation system producing a pencil beam with a thermal capture equivalent flux of about 10$$^8$$ns$$^{-1}$$cm$$^{-2}$$ at the target position and negligible neutron halo. The target was surrounded by an array of eight to ten anti-Compton shielded EXOGAM Clover detectors, four to six anti-Compton shielded large coaxial GASP detectors and two standard Clover detectors. For a part of the campaign the array was combined with 16 LaBr$$_{3}$$:(Ce) detectors from the FATIMA collaboration.

論文

$$beta$$-delayed fission of $$^{230}$$Am

Wilson, G. L.*; 武山 美麗*; Andreyev, A. N.; Andel, B.*; Antalic, S.*; Catford, W. N.*; Ghys, L.*; 羽場 宏光*; He${ss}$berger, F. P.*; Huang, M.*; et al.

Physical Review C, 96(4), p.044315_1 - 044315_7, 2017/10

 被引用回数:6 パーセンタイル:47.01(Physics, Nuclear)

The exotic decay process of $$beta$$-delayed fission has been studied in the neutron-deficient isotope $$^{230}$$Am at RIKEN, Japan. The $$^{230}$$Am nuclei were produced in the complete fusion reaction $$^{207}$$Pb($$^{27}$$Al,4n)$$^{230}$$Am and separated by using the GARIS gas-filled recoil ion separator. A lower limit for the $$beta$$-delayed fission probability larger than 0.30 was deduced, which so far is the highest value among all known nuclei exhibiting this decay mode.

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

 被引用回数:23 パーセンタイル:71.49(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

Volume-wise destruction of the antiferromagnetic Mott insulating state through quantum tuning

Frandsen, B. A.*; Liu, L.*; Cheung, S. C.*; Guguchia, Z.*; Khasanov, R.*; Morenzoni, E.*; Munsie, T. J. S.*; Hallas, A. M.*; Wilson, M. N.*; Cai, Y.*; et al.

Nature Communications (Internet), 7, p.12519_1 - 12519_8, 2016/08

 被引用回数:33 パーセンタイル:77.26(Multidisciplinary Sciences)

RENiO$$_3$$ (RE = rare-earth element) and V$$_2$$O$$_3$$ are archetypal Mott insulator systems. When tuned by chemical substitution (RENiO$$_3$$) or pressure (V$$_2$$O$$_3$$), they exhibit a quantum phase transition (QPT) between an antiferromagnetic Mott insulating state and a paramagnetic metallic state. Because novel physics often appears near a Mott QPT, the details of this transition, such as whether it is first or second order, are important. Here, we demonstrate through muon spin relaxation/rotation experiments that the QPT in RENiO$$_3$$ and V$$_2$$O$$_3$$ is first order: the magnetically ordered volume fraction decreases to zero at the QPT, resulting in a broad region of intrinsic phase separation, while the ordered magnetic moment retains its full value until it is suddenly destroyed at the QPT. These findings bring to light a surprising universality of the pressure-driven Mott transition, revealing the importance of phase separation and calling for further investigation into the nature of quantum fluctuations underlying the transition.

論文

$$B(E2;2^+_1rightarrow 0^+_1)$$ value in $$^{90}$$Kr

R$'e$gis, J.-M.*; Jolie, J.*; Saed-Samii, N.*; Warr, N.*; Pfeiffer, M.*; Blanc, A.*; Jentschel, M.*; K$"o$ster, U.*; Mutti, P.*; Soldner, T.*; et al.

Physical Review C, 90(6), p.067301_1 - 067301_4, 2014/12

 被引用回数:23 パーセンタイル:80.23(Physics, Nuclear)

A smooth onset of collectivity in $$^{88,92,94,96}$$Kr has been determined from reported $$B(E2;2^+_1rightarrow 0^+_1)$$ and E(2$$^+_1$$) values. This is in contrast to the sudden onset in even-even Zr, Mo, and Sr isotopes. Our objective was to complete the systematics by determining the $$B(E2;2^+_1rightarrow 0^+_1)$$ value in $$^{90}$$Kr, which was produced by cold-neutron-induced fission of $$^{235}$$U. The lifetime of the 2$$^+_1$$ state in $$^{90}$$Kr was measured via the electronic $$gamma - gamma$$ timing technique using the EXILL and FATIMA spectrometers. Based on the measured mean lifetime of $$tau$$ = 15(10) ps, the $$B(E2;2^+_1rightarrow 0^+_1)$$ value of 13$$^{+26}_{-5}$$ W.u. in $$^{90}$$Kr is determined for the first time and the smooth onset of deformation in the even-even Kr isotopes beyond neutron number N=50 is confirmed.

論文

Edge pedestal physics and its implications for ITER

鎌田 裕; Leonard, A. W.*; Bateman, G.*; Becoulet, M.*; Chang, C. S.*; Eich, T.*; Evans, T. E.*; Groebner, R. J.*; Guzdar, P. N.*; Horton, L. D.*; et al.

Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 8 Pages, 2007/03

周辺ペデスタル研究の進展とITERへ向けた予測について、最近の世界の研究をレビューする。周辺ペデスタル構造を決めるパラメータリンケージを明らかにするとともに、プラズマ過程と原子分子過程の両方がペデスタル幅を決定すること,周辺圧力勾配がピーリングバルーニング理論で系統的に説明できること,計測機器の進展によってELMの発展が明らかとなり非線形理論で説明可能であること,小振幅ELMの系統的同定がすすんだことなど、大きな発展があった。これらに基づいて、ITERのプラズマ性能の予測,ELMの小規模化等の検討が大きく進んだ。

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