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論文

$$alpha$$ decay of $$^{243}$$Fm$$_{143}$$ and $$^{245}$$Fm$$_{145}$$, and of their daughter nuclei

Khuyagbaatar, J.*; He${ss}$berger, F. P.*; Hofmann, S.*; Ackermann, D.*; Burkhard, H. G.*; Heinz, S.*; Kindler, B.*; Kojouharov, I.*; Lommel, B.*; Mann, R.*; et al.

Physical Review C, 102(4), p.044312_1 - 044312_8, 2020/10

https://doi.org/10.1103/PhysRevC.102.044312
 被引用回数：8 パーセンタイル：69.78(Physics, Nuclear)

Nuclear structure of $$^{243}$$Fm, $$^{245}$$Fm, and their daughter nuclei were investigated via detection of their radioactive decays, $$alpha$$, $$gamma$$, and spontaneous fission. Measured $$alpha$$-decay energies, half-lives, and branching ratios improve the literature data significantly. A signature for detection of the hitherto unknown $$^{235}$$Cm was found in the $$alpha$$-decay chains from $$^{243}$$Fm. Two groups of $$alpha$$ events with average energies of 6.69(2) MeV and 7.01(2) MeV and with a half-life of $$T_{1/2}$$ = 300$$^{+250}_{-100}$$, s are suggested to originate from $$^{235}$$Cm. Tentative decay schemes for $$^{243}$$Fm, $$^{239}$$Cf, $$^{235}$$Cm, and $$^{245}$$Fm, $$^{241}$$Cf isotopes are suggested based on the present experimental data. Systematical trends of single-particle states in $$N$$=141 isotones of $$Z$$ = 92-98 nuclei are discussed.

論文

Population of nuclides with Z$$ge$$98 in multi-nucleon transfer reactions of $$^{48}$$Ca+$$^{248}$$Cm

Devaraja, H. M.*; Heinz, S.*; Beliuskina, O.*; Hofmann, S.*; Hornung, C.*; M$"u$nzenberg, G.*; Ackermann, D.*; Gupta, M.*; Gambhir, Y. K.*; Henderson, R. A.*; et al.

European Physical Journal A, 55(2), p.25_1 - 25_9, 2019/02

https://doi.org/10.1140/epja/i2019-12696-3
 被引用回数：12 パーセンタイル：77.09(Physics, Nuclear)

The results for nuclei above curium, produced in multi-nucleon transfer reactions of $$^{48}$$Ca+$$^{248}$$Cm at the velocity filter SHIP of GSI Darmstadt, are presented. Spontaneous fission and $$alpha$$ activities have been used to study the population of nuclei with lifetimes ranging from few milliseconds to several days. We observed several, relatively neutron-rich isotopes with atomic numbers Z $$ge$$ 98; among them a weak 224 millisecond activity which we tentatively attributed to $$^{260}$$No. The measured cross-sections of the observed nuclei give hope that multi-nucleon transfer reactions are a way to reach new neutron-rich heavy and superheavy nuclei, which are not accessible in other reactions. We compare our results with data from earlier experiments and discuss limitations and future perspectives of the method.

論文

Observation of new neutron-deficient isotopes with Z$$ge$$92 in multinucleon transfer reactions

Devaraja, H. M.*; Heinz, S.*; Beliuskina, O.*; Comas, V. F.*; Hofmann, S.*; Hornung, C.*; M$"u$nzenberg, G.*; 西尾 勝久; Ackermann, D.*; Gambhir, Y. K.*; et al.

Physics Letters B, 748, p.199 - 203, 2015/09

AA2015-0304.pdf:0.78MB

https://doi.org/10.1016/j.physletb.2015.07.006
 被引用回数：66 パーセンタイル：97.01(Astronomy & Astrophysics)

In deep inelastic multinucleon transfer reactions of $$^{48}$$Ca +$$^{248}$$Cm we observed about 100 residual nuclei with proton numbers between Z =82 and Z =100. Among them, there are five new neutron-deficient isotopes: $$^{216}$$U, $$^{219}$$Np, $$^{223}$$Am, $$^{229}$$Am and $$^{233}$$Bk. As separator for the transfer products we used the velocity filter SHIP of GSI while the isotope identification was performed via the $$alpha$$-decay chains of the nuclei. These first results reveal that multinucleon transfer reactions together with here applied fast and sensitive separation and detection techniques are promising for the synthesis of new isotopes in the region of heaviest nuclei.

論文

In situ synthesis of volatile carbonyl complexes with short-lived nuclides

Even, J.*; Ackermann, D.*; 浅井 雅人; Block, M.*; Brand, H.*; Di Nitto, A.*; D$"u$llmann, Ch. E.*; Eichler, R.*; Fan, F.*; 羽場 宏光*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 303(3), p.2457 - 2466, 2015/03

https://doi.org/10.1007/s10967-014-3793-7
 被引用回数：15 パーセンタイル：77.56(Chemistry, Analytical)

金属カルボニル錯体の迅速その場合成を、核分裂や核融合反応によって生成される短寿命同位体を用いた実験によって実証した。高い反跳エネルギーを持つ短寿命核反応生成物を一酸化炭素分子と直接反応させることでカルボニル錯体を合成し、高い揮発性を持つ錯体のみをガス気流によって迅速に搬送し、化学分析・測定装置にかけて検出した。この手法を用いることで、Mo, Tc, Ru, Rh, W, Re, Os, Irの短寿命同位体の揮発性カルボニル錯体の合成に成功した。一方、HfとTaの揮発性錯体は検出されなかった。この手法は超重元素シーボーギウム(原子番号106)の化学研究に既に適用されており、また短寿命遷移金属同位体を用いた核科学研究の様々な分野への応用が今後期待される。

論文

The Reaction $$^{48}$$Ca + $$^{248}$$Cm $$rightarrow$$ $$^{296}$$116$$^{*}$$ studied at the GSI-SHIP

Hofmann, S.*; Heinz, S.*; Mann, R.*; Maurer, J.*; Khuyagbaatar, J.*; Ackermann, D.*; Antalic, S.*; Barth, B.*; Block, M.*; Burkhard, H. G.*; et al.

European Physical Journal A, 48(5), p.62_1 - 62_23, 2012/05

https://doi.org/10.1140/epja/i2012-12062-1
 被引用回数：167 パーセンタイル：98.87(Physics, Nuclear)

The synthesis of element 116 in the reactions of $$^{48}$$Ca+$$^{248}$$Cm was studied at the GSI-SHIP. Four decay chains from the isotope $$^{292}$$116 and one decay $$^{293}$$116 were detected at the reaction leading to the excitation energy of 40.9 MeV. The cross sections were 3.4 and 0.9 pb, respectively. The decay character reproduced the reported data at FLNR, Russia. In the $$alpha$$ decay chain, we observed the higher $$alpha$$-particle energy in the decay of $$^{289}$$114, which suggested the population and the decay of a quasiparitcle state.

論文

Di-nuclear systems studied with the velocity filter SHIP

Heinz, S.*; Comas, V.*; He${ss}$berger, F. P.*; Hofmann, S.*; Ackermann, D.*; Burkhard, H. G.*; Gan, Z.*; Heredia, J.*; Khuyagbaatar, J.*; Kindler, B.*; et al.

European Physical Journal A, 38(2), p.227 - 232, 2008/11

https://doi.org/10.1140/epja/i2008-10671-9
 被引用回数：24 パーセンタイル：78.21(Physics, Nuclear)

Various nuclear reactions like quasi-fission, fusion-fission or particle and cluster evaporation from excited compound nuclei were studied in heavy-ion reactions by using the velocity filter SHIP of GSI. The velocity distributions were measured for the heavier nuclei produced by bombarding $$^{25}$$Mg, $$^{64}$$Ni to the target nuclei $$^{206,207}$$Pb at energies of 5.9 MeV/A and 8.7 MeV/A. In addition to the evaporation residues produced in the fusion reactions, we found evidence for rotation and quasi-fission of nuclear molecules. The break-up of the systems showed a preferred clustering leading to isotopes in the region 84 $$le$$ $$Z$$ $$le$$ 88 and 122 $$le$$ $$N$$ $$le$$ 127.

論文

Spontaneous fission of neutron-deficient fermium isotopes and the new nucleus $$^{241}$$Fm

Khuyagbaatar, J.*; Hofmann, S.*; He${ss}$berger, F. P.*; Ackermann, D.*; Burkhard, H. G.*; Heinz, S.*; Kindler, B.*; Kojouharov, I.*; Lommel, B.*; Mann, R.*; et al.

European Physical Journal A, 37(2), p.177 - 183, 2008/08

https://doi.org/10.1140/epja/i2008-10608-4
 被引用回数：29 パーセンタイル：81.98(Physics, Nuclear)

Spontaneous fission of neutron-deficient fermium isotopes with neutron number N$$<$$144 was investigated. The nuclei were produced in fusion-evaporation reactions of $$^{40}$$Ar beams with $$^{204,206-208}$$Pb targets. The new isotope $$^{241}$$Fm was identified, and the half-life 0.73 ms was determined. The half-life was significantly longer than the neighboring even-even isotopes $$^{242,244}$$Fm, and the hindrance factor were calculated by the to be 1.1$$times$$10$$^{4}$$ for $$^{241}$$Fm and 5.2$$times$$10$$^{4}$$ for $$^{243}$$Fm, being associated with the lower tunneing probability for nuclei having nuclear spins. The result suggests also the possible production and detection of $$^{239,237}$$Fm becalsue of the stabilization against spontaneous fission.

論文

Positronium formation at low temperatures; The Role of trapped electrons

平出 哲也; Maurer, F. H. J.*; Eldrup, M.*

Radiation Physics and Chemistry, 58(5-6), p.465 - 471, 2000/06

https://doi.org/10.1016/S0969-806X(00)00201-2
 被引用回数：130 パーセンタイル：99.13(Chemistry, Physical)

陽電子が物質中に入射され、それ以前の陽電子によって形成された捕捉電子と反応することによって起こるポジトロニウム形成反応により低温域でポジトロニウム形成の増加が起こるとする、われわれが提唱したモデルを既に可視光の起こす効果によって確かめてきたが、さらに外部からの$$gamma$$線照射による捕捉電子の生成、ESRによるその濃度の同定により、くわしく議論する。また、このモデルが高分子以外の物質にも適用できることも示す。

論文

Free-volume distribution and positronium formation in amorphous polymers; Temperature and positron-irradiation-time dependence

C.L.Wang*; 平出 哲也; Maurer, F. H. J.*; Eldrup, M.*; N.J.Pedersen*

Journal of Chemical Physics, 108(11), p.4654 - 4661, 1998/03

https://doi.org/10.1063/1.475876
 被引用回数：153 パーセンタイル：97.11(Chemistry, Physical)

陽電子寿命測定法により2つのアモルファス高分子中の自由体積サイズの分布とオルソ-ポジトロニウム形成について研究を行った。ポリビニアアセテイト(PVAc)とポリメチルメタアクリレート(PMMA)を84Kからガラス転移温度以上まで測定し、84,149,224,249Kで200時間までの測定を行った。その結果、陽電子寿命測定から得られる自由体積分布は陽電子の照射時間に依存していないことがわかった。またオルソ-ポジトロニウム形成における温度及び陽電子照射の効果をスパーモデルにより議論した。

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