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論文

Fusion reaction $$^{48}$$Ca+$$^{249}$$Bk leading to formation of the element Ts (Z=117)

Khuyagbaatar, J.*; Yakushev, A.*; D$"u$llmann, Ch. E.*; Ackermann, D.*; Andersson, L.-L.*; 浅井 雅人; Block, M.*; Boll, R. A.*; Brand, H.*; Cox, D. M.*; et al.

Physical Review C, 99(5), p.054306_1 - 054306_16, 2019/05

$$^{48}$$Ca+$$^{249}$$B融合反応を用いて117番元素(Ts)合成実験を行い、117番元素に起因すると思われる4つの$$alpha$$崩壊連鎖を観測した。うち2つは長い崩壊連鎖で、$$^{294}$$Tsの$$alpha$$崩壊に起因するものと同定された。他の2つは短い崩壊連鎖で、$$^{293}$$Tsの$$alpha$$崩壊に起因すると考えると矛盾しない。今回の結果と過去の文献値を比較したところ、今回の我々の結果は過去の文献値をほぼ再現し、117番元素合成の事実を強く再確認する結果となった。

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

 被引用回数:1 パーセンタイル:14.11(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

Online chemical adsorption studies of Hg, Tl, and Pb on SiO$$_{2}$$ and Au surfaces in preparation for chemical investigations on Cn, Nh, and Fl at TASCA

Lens, L.*; Yakushev, A.*; D$"u$llmann, Ch. E.*; 浅井 雅人; Ballof, J.*; Block, M.*; David, H. M.*; Despotopulos, J.*; Di Nitto, A.*; Eberhardt, K.*; et al.

Radiochimica Acta, 106(12), p.949 - 962, 2018/12

 パーセンタイル:100(Chemistry, Inorganic & Nuclear)

半減期4$$sim$$49秒の短寿命同位体を用いて、水銀(Hg), タリウム(Tl), 鉛(Pb)の単一原子レベルでのSiO$$_{2}$$及びAu表面への固体吸着挙動をオンライン気相実験により調べた。超重元素Cn, Nh, Flの吸着エンタルピー測定のためのモデル実験として実施した。短寿命同位体はドイツ重イオン研究所の反跳核分離装置TASCAを用いて生成・分離した。生成核はヘリウムガス中に捕集された後、SiO$$_{2}$$あるいはAuで表面を覆われたSi検出器で作製されたガスクロマトグラフィーカラムへと導入した。短寿命Tl及びPb同位体は室温においてSiO$$_{2}$$表面に吸着し、Si検出器で測定することに成功した。一方、HgはSiO$$_{2}$$表面には吸着せず、Au表面に吸着した。この結果より、本実験のセットアップを用いることで短寿命Hg, Tl, Pb同位体の吸着特性を調べることができると証明され、この手法がCn, Nh, Flの実験にも適用できることが確認された。

論文

Radiochemical study of the kinematics of multi-nucleon transfer reactions in $$^{48}$$Ca + $$^{248}$$Cm collisions 10% above the Coulomb barrier

G$"o$tz, M.*; G$"o$tz, S.*; Kratz, J. V.*; D$"u$llmann, Ch. E.*; Mokry, Ch.*; Runke, J.*; Th$"o$rle-Pospiech, P.*; Wiehl, N.*; Sch$"a$del, M.; Ballof, J.*; et al.

Nuclear Physics A, 961, p.1 - 21, 2017/05

 被引用回数:3 パーセンタイル:39.76(Physics, Nuclear)

$$^{48}$$Ca + $$^{248}$$Cmの多核子移行反応の運動学を多層捕集箔法と放射化学分離法を用いて調べた。過去の研究で、生成核の同位体分布の幅が、標的よりも重い同位体より軽い同位体の方が広いことが知られており、標的よりも軽い同位体の方がエネルギーロスの大きな衝突の成分が多いためと解釈されてきた。しかし、本研究で両者の平均的な全運動エネルギー損失、すなわち平均励起エネルギーの大きさが測定され、両者に大きな違いがないことが明らかになった。このことは過去の解釈と矛盾するため、本研究では、高い励起エネルギーを持って生成される標的よりも重い同位体は核分裂によって失われる、という新しい解釈を提案した。

論文

Review of even element super-heavy nuclei and search for element 120

Hofmann, S.*; Heinz, S.*; Mann, R.*; Maurer, J.*; M$"u$nzenberg, G.*; Antalic, S.*; Barth, W.*; Burkhard, K. G.*; Dahl, L.*; Eberhardt, K.*; et al.

European Physical Journal A, 52(6), p.180_1 - 180_34, 2016/06

 被引用回数:59 パーセンタイル:7.58(Physics, Nuclear)

The reaction $$^{54}$$Cr+$$^{248}$$Cm was investigated at the velocity filter SHIP at GSI with the intention to study production and decay properties of isotopes of element 120. Three correlated signals were measured, which occurred within a period of 279 ms. The heights of the signals correspond with the expectations for a decay sequence starting with an isotope of element 120. However, a complete decay chain cannot be established, since a signal from the implantation of the evaporation residue cannot be identified unambiguously. Measured properties of the event chain are discussed in detail. The result is compared with theoretical predictions. Previously measured decay properties of even element super-heavy nuclei were compiled in order to find arguments for an assignment from the systematics of experimental data. In the course of this review, a few tentatively assigned data could be corrected. New interpretations are given for results which could not be assigned definitely in previous studies. The discussion revealed that the cross-section for production of element 120 could be high enough so that a successful experiment seems possible with presently available techniques. However, a continuation of the experiment at SHIP for a necessary confirmation of the results obtained in a relatively short irradiation of five weeks is not possible at GSI presently. In the summary and outlook section we also present concepts for the continuation of research in the field of super-heavy nuclei.

論文

Remarks on the fission barriers of super-heavy nuclei

Hofmann, S.*; Heinz, S.*; Mann, R.*; Maurer, J.*; M$"u$nzenberg, G.*; Antalic, S.*; Barth, W.*; Dahl, L.*; Eberhardt, K.*; Grzywacz, R.*; et al.

European Physical Journal A, 52(4), p.116_1 - 116_12, 2016/04

 被引用回数:14 パーセンタイル:10.27(Physics, Nuclear)

Shell-correction energies of super-heavy nuclei are approximated by using Q$$_{alpha}$$ values of measured decay chains. Five decay chains were analyzed, which start at the isotopes $$^{285}$$Fl, $$^{294}$$118, $$^{291}$$Lv, $$^{292}$$Lv and $$^{293}$$Lv. The data are compared with predictions of macroscopic-microscopic models. Fission barriers are estimated that can be used to eliminate uncertainties in partial fission half-lives and in calculations of evaporation-residue cross-sections. In that calculations, fission probability of the compound nucleus is a major factor contributing to the total cross-section. The data also provide constraints on the cross-sections of capture and quasi-fission in the entrance channel of the fusion reaction. Arguments are presented that fusion reactions for synthesis of isotopes of elements 118 and 120 may have higher cross-sections than assumed so far.

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

 被引用回数:25 パーセンタイル:6.41(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

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

 被引用回数:104 パーセンタイル:1.27(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.

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