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Graeger, R.*; Ackermann, D.*; Chelnokov, M.*; Chepigin, V.*; Dllmann, C. E.*; Dvorak, J.*; Even, J.*; Gorshkov, A.*; Heberger, F. P.*; Hild, D.*; et al.
Physical Review C, 81(6), p.061601_1 - 061601_5, 2010/06
被引用回数:43 パーセンタイル:89.96(Physics, Nuclear)The deformed doubly-magic nucleus Hs so far has only been observed as the four-neutron (4n) evaporation residue of the reaction Mg + Cm, where a maximum cross section of 3 pb was measured. Theoretical studies on the formation of Hs in the 4n evaporation channel of fusion reactions with different entrance channel asymmetry in the framework of a two-parameter Smoluchowski equation predict the reactions Ca + Ra and S + U to result in higher cross sections due to lower reaction Q-values. Here, we report on the first measurement of evaporation residues formed in the fusion reaction S + U and the observation of Hs, produced in the 4n evaporation channel, with a measured cross section of 0.8 pb at 51 MeV excitation energy. The one event cross section limits for the 3n, 4n, and 5n evaporation channels at 39 MeV excitation energy are 2.9 pb, while the cross section limits of the 3n and 5n channel at 51 MeV are 1.5 pb. This is significantly lower than the 5n cross section of the Mg + Cm reaction at a similar excitation energy.
Dvorak, J.*; Brchle, W.*; Chelnokov, M.*; Dllmann, Ch. E.*; Dvorakova, Z.*; Eberhardt, K.*; Jger, E.*; Krcken, R.*; Kuznetsov, A.*; 永目 諭一郎; et al.
Physical Review Letters, 100(13), p.132503_1 - 132503_4, 2008/04
Cm+Mg反応で生成する108番元素ハッシウム(Hs)同位体の生成断面積を迅速気相化学分離装置COMPACTを用いて測定した。入射重イオンMgのエネルギーを変化させCm(Mg, )反応の励起関数を求めたところ、比較的軽い重イオンとアクチノイドターゲットを組合せた反応、いわゆるHot-fusion反応での3蒸発過程が初めて観測された。この蒸発過程で生成する新しい超重核種Hsを同定することに成功した。
Dvorak, J.*; Brchle, W.*; Chelnokov, M.*; Dllmann, Ch. E.*; Dvorakova, Z.*; Eberhardt, K.*; Jger, E.*; Krcken, R.*; Kuznetsov, A.*; 永目 諭一郎; et al.
Physical Review Letters, 100(13), p.132503_1 - 132503_4, 2008/04
被引用回数:125 パーセンタイル:94.91(Physics, Multidisciplinary)By using the complete fusion reaction Mg+Cm, superheavy nuclide Hs was produced in the 3 evaporation channel. The experiment was carried out at UNILAC in GSI, Darmstadt, Germany. The fusion products were separated from other reaction products by using an online chemical separation and detection system. The new isotope Hs (Z=108) was identified by its decay properties and excitation functins as function of bombading energy of Mg, where excitation functions for 4 and 5 channel isotopes Hs were also observed. The Hs was produced at bombarding energy well below the Bass barrier. Because of the prolate deformation of U, Coulomb barrier decreases at polar collisions, allowing the system to fuse even in sub-barrier energies.
Dvorak, J.*; Brchle, W.*; Chelnokov, M.*; Dressler, R.*; Dllmann, Ch. E.*; Eberhardt, K.*; Gorshkov, V.*; Jger, E.*; Krcken, R.*; Kuznetsov, A.*; et al.
Physical Review Letters, 97(24), p.242501_1 - 242501_4, 2006/12
被引用回数:152 パーセンタイル:96.03(Physics, Multidisciplinary)超重核領域で理論的に予想されていた変形した二重魔法核Hsを初めて実験的に確認した。実験はドイツ重イオン研究所(GSI)で行った。Cm+Mg反応で合成されたHs同位体を、迅速気相化学分離法で選択に分離し、壊変エネルギーとそれに伴う15事象の壊変連鎖からHsを同定した。また壊変エネルギーから値をと決定した。Hsの生成断面積は約3pbであった。