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論文

Charge radii, moments, and masses of mercury isotopes across the $$N$$=126 shell closure

Day Goodacre, T.*; Afanasjev, A. V.*; Barzakh, A. E.*; Nies, L.*; Marsh, B. A.*; Sels, S.*; Perera, U. C.*; Ring, P.*; Wienholz, F.*; Andreyev, A. N.; et al.

Physical Review C, 104(5), p.054322_1 - 054322_18, 2021/11

 被引用回数:8 パーセンタイル:80.56(Physics, Nuclear)

Combining laser spectroscopy with Penning-trap mass spectroscopy at the Isolde facility at CERN, the charge radii of neutron-rich mercury isotopes $$^{202,203,206,207,208}$$Hg were successfully measured. Furthermore, more precise values for the masses of $$^{206,207,208}$$Hg was obtained, as well as the magnetic moment of $$^{207}$$Hg. These results were used to understand the systematics of Hg isotopes across the $$N$$=126 shell closure. Comparison with covariant density functional theory calculations revealed that in particular the 1$$i_{11/2}$$ and 2$$g_{9/2}$$ neutron orbitals affect the evolution of charge radii.

論文

Laser spectroscopy of neutron-rich $$^{207,208}$$Hg isotopes; Illuminating the kink and odd-even staggering in charge radii across the $$N$$ = 126 shell closure

Day Goodacre, T.*; Afanasjev, A. V.*; Barzakh, A. E.*; Marsh, B. A.*; Sels, S.*; Ring, P.*; 中田 仁*; Andreyev, A. N.; 他36名*

Physical Review Letters, 126(3), p.032502_1 - 032502_7, 2021/01

 被引用回数:27 パーセンタイル:94.67(Physics, Multidisciplinary)

The charge radii of $$^{207,208}$$Hg have been studied for the first time and those of $$^{202,203,206}$$Hg remeasured by laser spectroscopy at ISOLDE (CERN). The characteristic kink in the charge radii at the $$N$$ = 126 shell closure has been revealed, providing the first information on its behavior below the $$Z$$ = 82 shell closure. By a theoretical analysis, it is demonstrated, contrary to previous interpretations, that both the kink at $$N$$ = 126 and the odd-even staggering can be described predominantly at the mean-field level and that pairing does not need to play a crucial role in their origin.

論文

$$alpha$$-decay branching ratio of $$^{180}$$Pt

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

 被引用回数:5 パーセンタイル:53.56(Physics, Nuclear)

$$^{180}$$Ptの基底状態から娘核$$^{176}$$Osの基底状態への$$alpha$$崩壊分岐比を0.52(5)%と、過去の値と比較してより高精度で再決定した。$$^{180}$$PtはCERN-ISOLDE実験施設において$$^{180}$$Hgを単離し、その$$beta$$崩壊孫核種として生成した。今回の結果を用いて導出した$$alpha$$崩壊の換算崩壊幅は、中性子欠損Pt同位体の$$alpha$$崩壊幅の系統性について新しい描像を与えることとなった。

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:54.59(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:77.66(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

Shape staggering of midshell mercury isotopes from in-source laser spectroscopy compared with density-functional-theory and Monte Carlo shell-model calculations

Sels, S.*; Day Goodacre, T.*; Marsh, B. A.*; Pastore, A.*; Ryssens, W.*; 角田 佑介*; Althubiti, N.*; Andel, B.*; Andreyev, A. N.; 他39名*

Physical Review C, 99(4), p.044306_1 - 044306_17, 2019/04

 被引用回数:32 パーセンタイル:95.84(Physics, Nuclear)

Neutron-deficient $$^{177-185}$$Hg isotopes were studied using in-source laser resonance-ionization spectroscopy at the CERN-ISOLDE radioactive ion-beam facility. The endpoint of the odd-even nuclear shape staggering in mercury was observed directly by measuring the isotope shifts and hyperfine structures of $$^{177-185}$$Hg. Changes in the mean-square charge radii for all mentioned isotopes, magnetic dipole, and electric quadrupole moments of the odd-$$A$$ isotopes and arguments in favor of $$I = 7/2$$ spin assignment for $$^{177,179}$$Hg were deduced. Experimental results are compared with density functional theory (DFT) and Monte Carlo shell model (MCSM) calculations. DFT calculations using Skyrme parametrizations predict a jump in the charge radius around the neutron $$N = 104$$ midshell, with an odd-even staggering pattern related to the coexistence of nearly degenerate oblate and prolate minima. This near-degeneracy is highly sensitive to many aspects of the effective interaction, a fact that renders perfect agreement with experiments out of reach for current functionals. MCSM calculations of states with the experimental spins and parities show good agreement for both electromagnetic moments and the observed charge radii. A clear mechanism for the origin of shape staggering within this context is identified: a substantial change in occupancy of the proton $${pi}h_{9/2}$$ and neutron $${nu}i_{13/2}$$ orbitals.

論文

Characterization of the shape-staggering effect in mercury nuclei

Marsh, B. A.*; Day Goodacre, T.*; 角田 佑介*; Andreyev, A. N.; 他41名*

Nature Physics, 14(12), p.1163 - 1167, 2018/12

 被引用回数:82 パーセンタイル:96.77(Physics, Multidisciplinary)

In rare cases, the removal of a single proton (Z) or neutron (N) from an atomic nucleus leads to a dramatic shape change. These instances are crucial for understanding the components of the nuclear interactions that drive deformation. The mercuryisotopes (Z = 80) are a striking example: their close neighbours, the lead isotopes (Z = 82), are spherical and steadily shrink with decreasing N. The even-mass (A = N + Z) mercury isotopes follow this trend. The odd-mass mercury isotopes $$^{181,183,185}$$Hg, however, exhibit noticeably larger charge radii. Due to the experimental difficulties of probing extremely neutron-deficient systems, and the computational complexity of modelling such heavy nuclides, the microscopic origin of this unique shape staggering has remained unclear. Here, by applying resonance ionization spectroscopy, mass spectrometry and nuclear spectroscopy as far as $$^{177}$$Hg, we determine $$^{181}$$Hg as the shape-staggering endpoint. By combining our experimental measurements with Monte Carlo shell model calculations, we conclude that this phenomenon results from the interplay between monopole and quadrupole interactions driving a quantum phase transition, for which we identify the participating orbitals. Although shape staggering in the mercury isotopes is a unique and localized feature in the nuclear chart, it nicely illustrates the concurrence of single-particle and collective degrees of freedom at play in atomic nuclei.

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