原子核的同位旋对碎裂产物的影响

ISOSPIN EFFECT ON PRODUCTS OF NUCLEAR FRAGMENTATION 

用同位旋相关的晶格气体模型系统地研究了Z =5 4的同位素和A =12 9的同质异位素热发射体的粒子发射的特性 ,阐述了发射体系的同位旋对中子、质子和带电粒子产额 ,以及轻粒子的同位素比及同位素对的比的影响 .同时 ,还比较了在同位旋相关作用势下和同位旋不相关作用势下碎片产物特性的差异 .发现了不同质量区间 (轻粒子、中等质量碎片和重余核 )的产物的平均中子 质子比 <N/Z >,在同位旋相关的或不相关的作用下它们有十分不同的温度依赖性 .发现核气态 (轻粒子 )的 <N/Z >要大于核液态 (重余核 )的 <N/Z >,也就是说在液气共存时的气态有更大的同位旋非对称性 .对于同位旋不相关作用势的情况 。

The isospin effects on the cluster emission are explored for the disassembling isotopic sources of Z=54 and for the isobaric sources of A=129 in the framework of the isospin dependent lattice gas model. The multiplicity of emitted particles, the isotopic and isobaric ratios of light particles show the strong dependence on the isospin of the dissociation source, but the double ratios of light isotopes are insensitive to the isospin. The former reflects directly the chemical composition and the latter indicates the chemical equilibrium of the source. In addition, the features of products in nuclear disassembly with an isospin independent potential is also investigated and used to compare the results from the above isospin dependent potential. It is found that there are very different temperature dependences of the mean ratio of N to Z(<N/Z>) in the different mass intervals (light particles, intermediate mass fragments and heavy residues). <N/Z> in nuclear gas phase is larger than that in nuclear liquid phase, i.e.,the nuclear gas phase has larger isospin asymmetry as the liquid and the gas coexists. We also found that the isotopic ratios are nearly independent of the isospin of emitter provided that the isospin independent potential is used.