Measurements of cross sections and decay properties of the isotopes of elements 112, 114, and 116 produced in the fusion reactions 233,238U, 242Pu, and 248Cm+48Ca -: art. no. 064609
Measurements of cross sections and decay properties of the isotopes of elements 112, 114, and 116 produced in the fusion reactions 233,238U, 242Pu, and 248Cm+48Ca -: art. no. 064609
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DOI：
10.1103/physrevc.70.064609
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发表时间：
2004-12-01
影响因子：
3.1
通讯作者：
Vesnovskii, SP
中科院分区：
文献类型：
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作者：
Oganessian, YT;Utyonkov, VK;Vesnovskii, SP
我们研究了同位素（282,283）112和（286,287）114的生成截面与复合核（286）112和（290）114的激发能的关系。测得U-238(Ca-48,xn)(286-x)112反应的xn-蒸发通道的最大横截面值分别为sigma(3n)=2.5(-1.1)(+1.8) pb和sigma(4n)=0.6(-0.5)(+1.6) pb；对于反应Pu-242(Ca-48,xn)(290-x)114: sigma（2n）近似于0.5 pb, sigma(3n)=3.6(-1.7)(+3.4) pb, sigma(4n)=4.5(-1.9)(+3.6) pb。在E*=34.9=2.2 MeV的U-233(ca -48,2-4n)(277-279)112反应中，我们测得sigma（xn）的上截面极限小于或等于0.6 pb。观察到的与最大蒸发残余横截面sigma(ER)（E*）相关的激发能显著高于与计算的库仑势垒相关的激发能，这可能是由反应入口通道中变形靶核的取向引起的。锕系元素靶与Ca-48的反应中sigma（ER）的增加与受激化合物核在更接近闭合中子壳层N=184时生存能力的预期增加是一致的。在目前的工作中，我们检测到在已知原子核（282）112、（283）112、（286）114、（287）114和（288）114的衰变中产生了33个衰变链。在（287）114（α）—>(283)112（α）—>(279)110（SF）的衰变中，在22个案例中的两个，我们观察到四个和五个连续的α跃变的衰变链，最终以（271）Sg (T- α /SF=2.4（-1.0)(+4.3) min）和（267）Rf （T（SF）类似于2.3 h）的自发裂变结束，比以前报道的更长。我们观察到新的核素（292）116 (t - α =18（-6)(+16) ms, e - α =10.66+/-0.07 MeV）在Cm-248靶上的辐照能量高于以往的实验。对Z=104 ~ 118的核素的核衰变性质进行了观测，并与理论核质量计算和自发裂变性质的系统趋势进行了比较。总的来说，他们给出了18种偶数-Z富中子核素（Z=104-118和N=163-177）衰变的一致模式。实验采用杜布纳充气反冲分离器，利用FLNR （JINR, Dubna）的U400回旋加速器输送重离子束。
We have studied the dependence of the production cross sections of the isotopes (282,283)112 and (286,287)114 on the excitation energy of the compound nuclei (286)112 and (290)114. The maximum cross section values of the xn-evaporation channels for the reaction U-238(Ca-48,xn)(286-x)112 were measured to be sigma(3n)=2.5(-1.1)(+1.8) pb and sigma(4n)=0.6(-0.5)(+1.6) pb; for the reaction Pu-242(Ca-48,xn)(290-x)114: sigma(2n)similar to0.5 pb, sigma(3n)=3.6(-1.7)(+3.4) pb, and sigma(4n)=4.5(-1.9)(+3.6) pb. In the reaction U-233(Ca-48,2-4n)(277-279)112 at E*=34.9=2.2 MeV we measured an upper cross section limit of sigma(xn)less than or equal to0.6 pb. The observed shift of the excitation energy associated with the maximum sum evaporation residue cross section sigma(ER)(E*) to values significantly higher than that associated with the calculated Coulomb barrier can be caused by the orientation of the deformed target nucleus in the entrance channel of the reaction. An increase of sigma(ER) in the reactions of actinide targets with Ca-48 is consistent with the expected increase of the survivability of the excited compound nucleus upon closer approach to the closed neutron shell N=184. In the present work we detected 33 decay chains arising in the decay of the known nuclei (282)112, (283)112, (286)114, (287)114, and (288)114. In the decay of (287)114(alpha)-->(283)112(alpha)-->(279)110(SF), in two cases out of 22, we observed decay chains of four and five sequential alpha transitions that end in spontaneous fission of (271)Sg (T-alpha/SF=2.4(-1.0)(+4.3) min) and (267)Rf (T(SF)similar to2.3 h), longer decay chains than reported previously. We observed the new nuclide (292)116 (T-alpha=18(-6)(+16) ms,E-alpha=10.66+/-0.07 MeV) in the irradiation of the Cm-248 target at a higher energy than in previous experiments. The observed nuclear decay properties of the nuclides with Z=104-118 are compared with theoretical nuclear mass calculations and the systematic trends of spontaneous fission properties. As a whole, they give a consistent pattern of decay of the 18 even-Z neutron-rich nuclides with Z=104-118 and N=163-177. The experiments were performed with the heavy-ion beam delivered by the U400 cyclotron of the FLNR (JINR, Dubna) employing the Dubna gas-filled recoil separator.