Decay of excited nuclei produced in $^{78,82}$Kr + $^{40}$Ca reactions at 5.5 MeV/nucleon
G. Ademard, J. P. Wieleczko, J. Gomez Del Campo, M. La Commara, E. Bonnet, M. Vigilante, A. Chbihi, J. D. Frankland, E. Rosato, G. Spadaccini, Sh. A. Kalandarov… 展开作者
G. Ademard, J. P. Wieleczko, J. Gomez Del Campo, M. La Commara, E. Bonnet, M. Vigilante, A. Chbihi, J. D. Frankland, E. Rosato, G. Spadaccini, Sh. A. Kalandarov, C. Beck, S. Barlini, B. Borderie, R. Bougault, R. Dayras, G. De Angelis, J. De Sanctis, V. L. Kravchuk, P. Lautesse, N. Le Neindre, J. Moisan, A. D'onofrio, M. Parlog, D. Pierroutsakou, M. F. Rivet, M. Romoli, R. Roy, G. G. Adamian, N. V. Antonenko
备注：
2 tables, 14 figures, accepted for publication in Physical Review C
研究了5.5MeV/核子的$^{78,82}$ Kr + $^{40}$ Ca反应中激发核的衰变模式.通过$4π$ INDUSTRY阵列测量带电产物。原子序数为3 $\le Z \le$ 28的碎片的动能谱和角分布表明高度弛豫，并与裂变现象相一致。结构效应的持久性从元素截面（$σ_{Z}$）以及光碎片产率的强奇偶交错（o-e-s）中得到证明。交错的幅度并不显著地取决于发射系统的中子含量。碎片粒子的巧合表明，在非常不对称的裂变轻合作伙伴发出冷或激发能量低于粒子发射阈值。$^{78}$ Kr + $^{40}$ Ca反应的蒸发残留物截面略高于在$^{82}$ Kr + $^{40}$ Ca反应中测量的蒸发残留物截面。对于具有最低中子-质子比的反应，类裂变成分大$\sim$ 25%。这些实验特征面临的理论模型的预测。Hauser-Feshbach方法包括在基态和激发态发射高达$Z$ = 14的碎片，但不能解释$σ_{Z}$的主要特征。对于这两个反应，过渡态形式主义合理地再现了$Z$ -分布的片段与电荷12 $\le Z \le$ 28。然而，该模型严重高估了轻碎片横截面，并且不能解释6 $\le Z \le$ 10的产率的o-e-s。整个$Z$分布的形状和轻碎片产额的o-e-s在处理蒸发、聚变-裂变和准裂变过程之间的竞争的双核系统框架内得到满意的再现。该模型表明，重碎片主要来自准裂变，而轻碎片主要由聚变填充。对16 $\le Z \le$ 22的横截面的低估可能表明除了捕获过程之外的机制。
英文摘要：
Decay modes of excited nuclei are investigated in $^{78,82}$Kr + $^{40}$Ca reactions at 5.5 MeV/nucleon. Charged products were measured by means of the $4π$ INDRA array. Kinetic-energy spectra and angular distributions of fragments with atomic number 3 $\le Z \le$ 28 indicate a high degree of relaxation and are compatible with a fission-like phenomenon. Persistence of structure effects is evidenced from elemental cross-sections ($σ_{Z}$) as well as a strong odd-even-staggering (o-e-s) of the light-fragment yields. The magnitude of the staggering does not significantly depend on the neutron content of the emitting system. Fragment-particle coincidences suggest that the light partners in very asymmetric fission are emitted either cold or at excitation energies below the particle emission thresholds. The evaporation residue cross-section of the $^{78}$Kr + $^{40}$Ca reaction is slightly higher than the one measured in $^{82}$Kr + $^{40}$Ca reaction. The fission-like component is larger by $\sim$ 25% for the reaction having the lowest neutron-to-proton ratio. These experimental features are confronted to the predictions of theoretical models. The Hauser-Feshbach approach including the emission of fragments up to $Z$ = 14 in their ground states as well as excited states does not account for the main features of $σ_{Z}$. For both reactions, the transition-state formalism reasonably reproduces the $Z$-distribution of the fragments with charge 12 $\le Z \le$ 28. However, this model strongly overestimates the light-fragment cross-sections and does not explain the o-e-s of the yields for 6 $\le Z \le$ 10. The shape of the whole $Z$-distribution and the o-e-s of the light-fragment yields are satisfactorily reproduced within the dinuclear system framework which treats the competition between evaporation, fusion-fission and quasifission processes. The model suggests that heavy fragments come mainly from quasifission while light fragments are predominantly populated by fusion. An underestimation of the cross sections for 16 $\le Z \le$ 22 could signal a mechanism in addition to the capture process.
Multiplicity fluctuation analysis of target residues in nucleus-emulsion collisions at a few hundred MeV/nucleon
采用标度阶乘矩方法，分别在二维正态相空间和累积变量空间中研究了290 A MeV ~（12）C-AgBr、400 A MeV ~（12）C-AgBr、400 A MeV ~（20）Ne-AgBr和500 A MeV ~（56）Fe-AgBr相互作用中靶蒸发碎片的多重数涨落.结果表明，在正常相空间中，当q值较低时，比例阶乘矩（ln<Fq>）随相空间分割数（lnM）的增加而线性增加，当q值较高时，比例阶乘矩（ln）随lnM的增加而线性增加，然后趋于饱和或减小;在累积变量空间<Fq>中，比例阶乘矩（ln）随lnM的增加而线性减小，这表明在我们的数据集中没有观察到非统计多重数涨落的证据.因此，正态变量空间分析结果中的任何波动都是由单颗粒密度分布的不均匀性引起的。
Forward-backward multiplicity correlations of target fragments in nucleus-emulsion collisions at a few hundred MeV/nucleon
本文研究了150 A MeV He-乳胶、290 A MeV C-乳胶、400 A MeV C-乳胶、400 A MeV Ne-乳胶和500 A MeV Fe-乳胶相互作用中靶蒸发碎片（黑径迹粒子）和靶反冲质子（灰径迹粒子）的前向-后向多重数和关联。结果表明，灰、黑和重电离径迹粒子的前向和后向平均多重数随靶尺寸的增大而增大。前向黑径迹粒子、后向黑径迹粒子和后向灰径迹粒子的平均多重数与粒子大小和能量无关，但前向灰径迹粒子的平均多重数随粒子大小和能量的增加而增加。后向灰径迹粒子多重数分布服从指数衰减规律，衰减常数随目标尺寸的增大而减小。前后向多重数关联遵循线性规律，与弹丸尺寸和能量无关，在某些重目标数据集中观察到饱和效应。
Persistence of odd-even staggering in charged fragment yields from the 112Sn+58Ni collision at 35 MeV/nucleon
本文研究了35 MeV/核子的112 Sn +58 Ni半周边和中心碰撞产生的碎片的电荷分布的奇偶交错效应。对于Z<16的碎片，观察到偶数电荷的明显过量产生，其对于较重的碎片减少。在外围碰撞中，交错效应持续到Z约40。对于轻碎片，交错似乎是基本上独立的碰撞的中心性，这表明它主要是有关的最后几个步骤，在热核衰变。
Contemporary presence of dynamical and statistical production of intermediate mass fragments in midperipheral $^{58}$Ni+$^{58}$Ni collisions at 30 MeV/nucleon
在INFN超导回旋加速器上对30 MeV/核子的$^{58}Ni+^{58}Ni$反应进行了实验研究。在中周边碰撞中，观察到大量碎片（4 $\le$ Z $\le$ 12）的产生，这与弹状残留物的统计碎片化和颈部的动态形成相一致，加入了弹状和靶状残留物。来自这些不同过程的碎片在电荷分布和同位素组成方面都不同。特别是，它表明，这些机制导致片段生产的行为，同时在同一事件。
A nucleation model analysis of neck emission yields in 124Sn+112,124Sn reactions at 26 MeV/nucleon
最近的分析实验三元裂变碎片产额使用核调节的统计平衡模型再现观察到的产额具有相当好的精度。在本工作中，同样的方法被应用到颈部发射在周边和中部周边124 Sn +112，124 Sn碰撞在26 A MeV。该模型能够合理地再现锂到硅同位素的产额与现实的时间和温度值。比较了由本数据得到的平衡常数与以前得到的242 Pu三裂变的平衡常数。
