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論文

$$beta$$-delayed fission of isomers in $$^{188}$$Bi

Andel, B.*; Andreyev, A. N.; Antalic, S.*; Al Monthery, M.*; Barzakh, A.*; Bissell, M. L.*; Chrysalidis, K.*; 他29名*

Physical Review C, 102(1), p.014319_1 - 014319_12, 2020/07

$$beta$$-delayed fission ($$beta$$DF) decay of a low-spin (ls) and a high-spin (hs) isomer in $$^{188}$$Bi was studied at the ISOLDE facility at CERN. Their $$beta$$DF partial half-lives were determined: $$T_{rm 1/2p}$$, $$beta$$DF($$^{188}$$Bi$$^{hs}$$)= 5.6(8) $$times$$ 10$$^{3}$$ s and $$T_{rm 1/2p}$$, $$beta$$DF($$^{188}$$Bi$$^{ls}$$)=1.7(6) $$times$$ 10$$^{3}$$ s. This work is the first $$beta$$DF study of two states in one isotope and allows the spin dependence of low-energy fission to be explored. The fission fragment mass distribution of a daughter nuclide $$^{188}$$Pb, following the $$beta$$ decay of the high-spin isomer, was deduced and indicates a mixture of symmetric and asymmetric fission modes.

論文

Shape coexistence in $$^{187}$$Au studied by laser spectroscopy

Barzakh, A. E.*; Atanasov, D.*; Andreyev, A. N.; Al Monthery, M.*; Althubiti, N. A.*; Andel, B.*; Antalic, S.*; Blaum, K.*; 他34名*

Physical Review C, 101(6), p.064321_1 - 064321_7, 2020/06

Hyperfine-structure parameters and isotope shift of the $$9/2^{-}$$ isomeric state in $$^{187}$$Au relative to $$^{197}$$Au for the 267.6-nm atomic transition have been measured for the first time using the in-source resonance-ionization spectroscopy technique. The magnetic dipole moment and change in the mean-square charge radius for this $$9/2^{-}$$ isomer have been deduced. The observed large isomer shift relative to the $$1/2^{+}$$ ground state in $$^{187}$$Au confirms the occurrence of the shape coexistence in $$^{187}$$Au proposed earlier from the analysis of the nuclear spectroscopic data and particle plus triaxial rotor calculations. The analysis of the magnetic moment supports the previously proposed $$9/2^{-}$$, $$1/2^{-}$$[541] assignment at moderate prolate deformation for $$^{187}$$Au$$^{m}$$.

論文

Hyperfine anomaly in gold and magnetic moments of $$I^{pi}$$ = 11/2$$^{-}$$ gold isomers

Barzakh, A. E.*; Atanasov, D.*; Andreyev, A. N.; Al Monthery, M.*; Althubiti, N. A.*; Andel, B.*; Antalic, S.*; Blaum, K.*; 他39名*

Physical Review C, 101(3), p.034308_1 - 034308_9, 2020/03

Hyperfine-structure constants for the $$I^{pi}$$ = 11/2$$^{-}$$ gold isomers $$^{177,191,193,195}$$Au$$^{m}$$ have been measured at CERN-ISOLDE, using the in-source laser resonance-ionization spectroscopy technique. From the measured hyperfine constants the differences between hyperfine anomalies have been deduced. These differential hyperfine anomaly values have been used to determine the hyperfine anomaly relative to the stable $$^{197}$$Au with advanced atomic calculations. Magnetic dipole moments for the gold isomers in question have been deduced, taking into account the corresponding relative hyperfine-anomaly values. It has been shown that the commonly used prescription for the extraction of the magnetic moment values for the gold isotopes should be reconsidered. The magnetic moments calculated by this prescription have been reevaluated by properly accounting for the hyperfine anomaly, which is as large as 10% for several gold isotopes.

論文

In-source laser spectroscopy of dysprosium isotopes at the ISOLDE-RILIS

Chrysalidis, K.*; Barzakh, A. E.*; Ahmed, R.*; Andreyev, A. N.; Ballof, J.*; Cubiss, J. G.*; Fedorov, D. V.*; Fedosseev, V. N.*; Fraile, L. M.*; Harding, R. D.*; et al.

Nuclear Instruments and Methods in Physics Research B, 463, p.472 - 475, 2020/01

 被引用回数:0 パーセンタイル:100(Instruments & Instrumentation)

放射壊変によって生成された多数のジスプロシウム同位体について、ISOLDEのレーザー共鳴イオン源(RILIS)を用いてイオン源内レーザー分光法によって研究した。$$^{152}$$Dyに対する相対的な同位体シフトを$$4f^{10}6s^{2}~^{5}I_{8}$$ (gs) $$rightarrow$$ $$4f^{10}6s6p~(8,1)^{o}_{8}$$共鳴遷移を用いて測定した。電子的因子Fとマスシフト因子Mを導出し、それらを使って$$^{rm 145m}$$Dyと$$^{rm 147m}$$Dyの平均自乗荷電半径の変化を初めて決定した。

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:2 パーセンタイル:25.8(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

$$alpha$$-decay properties of $$^{200,202}$$Fr

Ghys, L.*; Andreyev, A. N.; Huyse, M.*; Van Duppen, P.*; Antalic, S.*; Barzakh, A.*; Capponi, L.*; Cocolios, T. E.*; Cubiss, J.*; Derkx, X.*; et al.

Physical Review C, 100(5), p.054310_1 - 054310_13, 2019/11

 被引用回数:4 パーセンタイル:22.15(Physics, Nuclear)

The aim of this work was to investigate the $$alpha$$-decay properties of $$^{200,202}$$Fr and daughter products. Neutron-deficient francium nuclei are produced at ISOLDE-CERN bombarding a UCx target with 1.4 GeV protons. Due to the very high statistics and the high beam purity, improved decay data for $$^{202}$$Fr and its daughters were obtained. The observation of crossover transitions positioned the isomeric high-spin level of $$^{198}$$At at an excitation energy of 265(3) keV. Half-life values of 4.47(5) s and 1.28(10) s were extracted for the ground state and isomeric state of $$^{198}$$At and 52(3) ms for the ground-state decay of $$^{200}$$Fr.

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:3 パーセンタイル:22.15(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:3 パーセンタイル:22.15(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

Change in structure between the $$I$$=1/2 states in $$^{181}$$Tl and $$^{177,179}$$Au

Cubiss, J. G.*; Barzakh, A. E.*; Andreyev, A. N.; 他57名*

Physics Letters B, 786, p.355 - 363, 2018/11

 被引用回数:8 パーセンタイル:15.62(Astronomy & Astrophysics)

The first accurate measurements of the $$alpha$$-decay branching ratio and half-life of the I$$^pi$$=1/2$$^{+}$$ ground state in $$^{181}$$Tl have been made, along with the first determination of the magnetic moments and I=1/2 spin assignments of the ground states in $$^{177,179}$$Au. The results are discussed within the complementary systematics of the reduced $$alpha$$-decay widths and nuclear g factors of low-lying, I$$^pi$$=1/2$$^{+}$$states in the neutron-deficient lead region. The findings shed light on the unexpected hindrance of the 1/2$$^{+}$$ $$rightarrow$$ 1/2$$^{+}$$, $$^{181}$$Tl$$^{g}$$ $$rightarrow$$ $$^{177}$$Au$$^{g}$$ $$alpha$$decay, which is explained by a mixing of $$pi$$3s$$_{1/2}$$and $$pi$$2d$$_{3/2}$$ configurations in $$^{177}$$Au$$^{g}$$, whilst $$^{181}$$Tl$$^{g}$$ remains a near-pure $$pi$$3s$$^{1/2}$$. This conclusion is inferred from the g factor of $$^{177}$$Au$$^{g}$$ which has an intermediate value between those of $$pi$$3s$$_{1/2}$$ and $$pi$$2d$$_{3/2}$$ states. A similar mixed configuration is proposed for the I$$^pi$$=1/2$$^{+}$$ ground state of $$^{179}$$Au. This mixing may provide evidence for triaxial shapes in the ground states in these nuclei.

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

 被引用回数:0 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:14 パーセンタイル:12.29(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:7 パーセンタイル:36.29(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:7 パーセンタイル:41.23(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:7 パーセンタイル:46.64(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

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:17 パーセンタイル:21.7(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

$$beta$$-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:29 パーセンタイル:10.63(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

 被引用回数:14 パーセンタイル:26.8(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:139 パーセンタイル:3.04(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

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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