The extreme back-angle evaporation spectra of alpha, lithium, beryllium, boron and carbon from different compound nuclei near A=100 (EX=76-210 MeV) have been compared with the predictions of standard statistical model codes such as 'CASCADE' and 'GEMINI'. It was found that the shapes of the alpha spectra agree well with the predictions of the statistical models. However the spectra of lithium, beryllium, boron and carbon show significantly gentler slopes implying higher temperature of the residual nuclei, even though the spectra satisfy all other empirical criteria of statistical emissions. The observed slope anomaly was found to be largest for lithium and decreases at higher excitation energy. These results could not be understood by adjusting the parameters of the statistical models or from reaction dynamics and might require examining the statistical model from a quantum mechanical perspective.
Multifragmentation vs. Evaporation vs. Binary-Decay in Fragment Production
本文介绍了LANL完成改进的级联激子模型(CEM03.01)和洛斯阿拉莫斯夸克胶子弦模型(LAQGSM.03.01)的“S”和“G”版本的部分进展报告。“S”版本使用Botvina等人的统计多重碎裂模型(SMM)考虑了在2A MeV以上的激发能的反应预平衡阶段后产生的复合核的碎裂。(“S”代表SMM),而“G”版本使用Charity等人的裂变类二元衰变模型GEMINI描述反应的蒸发/裂变阶段。(“G”代表GEMINI),而不是使用Furihata的广义蒸发模型GEM 2,该模型已纳入这些规范的标准版本中。本文分析了最近的660 MeV p +129 I和3.65 GeV p +112 Sn JINR测量结果,COSY新的1.2 GeV p +(从Al到Th的13个核)数据,GSI 300 MeV和1 GeV p +56 Fe逆运动学测量数据,以及GSI新的1 GeV/核子124 He和136 He + Pb数据。为了更好地了解碎片生产的机制,我们讨论了几个计算,但尚未测量的这些反应,这是预测SMM,GEMINI,和GEM 2是完全不同的产品的运动学特征。我们发现这些运动学量是潜在的有用的区分这些反应机制,如果它们可以在未来的实验中测量。
Single-proton removal reaction in the IQMD+GEMINI model benchmarked by elemental fragmentation cross sections of $^{29-33}\mathrm{Si}$ on carbon at $\sim$230~MeV/nucleon
Fission Hindrance in hot 216Th: Evaporation Residue Measurements
用ATLAS碎片质量分析仪测量了能量为165、174、185、196、205、215、225、236、246和257 MeV的32 S +184 W的聚变蒸发残余物截面。与统计模型计算的数据进行了比较,发现需要一个随激发能增加的核耗散强度来再现激发函数。与以前发表的数据的比较表明,耗散强度强烈依赖于壳结构的核系统。
The effect of the neutron and proton numbers ratio in colliding nuclei at formation of the evaporation residues in the $^{34}$S+$^{208}$Pb and $^{36}$S+$^{206}$Pb reactions
Study of Isoscaling with Statistical Multifragmentation Models
不同的统计多重碎裂模型已被用来研究等标度,即从两个反应的同位素比因子分解成质子和中子数的逸度项,R 21(N,Z)= Y 2(N,Z)/Y 1(N,Z)=C*exp(a*N+b*Z)。尽管由于激发碎片的蒸发,初级同位素分布与最终分布有很大不同,但a和b的值不会受到连续衰变的影响。A被示出主要对发射源的质子和中子组成敏感,并且可以用于研究核碰撞中的同位旋依赖性质,例如非对称核物质的状态方程中的对称能。