25MeV/u　^(40)Ar+^(115)In,^(58)Ni,^(27)Al反应中前中角区碎片角分布和元素Z分布

Angular and Z Distributions of the Fragments at Forward and Intermediate Angles in the Reaction of 25MeV/ u ^(40) Ar + ^(115) In, ^(58) Ni, ^(27)Al

测量了 ２５ＭｅＶ／ｕ４０ Ａｒ＋１１５ Ｉｎ，５８ Ｎｉ，２７ Ａ１反应前中角区出射碎片的角分布和 元素 Ｚ分布．用改进的量子分子动力学（ＭＱＭＤ）模型研究了碎片的角分布和 Ｚ 分布．理论计算值和实验值整体上符合得很好，但在前角区，ＭＱＭＤ模型低估 了碎片的产额，在中角区对于Ｚ接近弹核的碎片，理论计算值比实验值偏高．碎 片产物的角分布和Ｚ分布还与统计蒸发模型ＧＥＭＩＮＩ进行了比较，结果表明，在 前角区平衡蒸发成份所占的比例很小，中角区所占的比例有所增加，但仍然是较 小的比例．同时发现平衡蒸发成份随着出射碎片核电荷数Ｚ的减小而逐渐减 少．

The angular & Z distributions of foe fragments emitted in the forward and intermediary angles are measured at the reaction of 25 MeV/ u ~40 Ar + ~115 In, ~58Ni, ~27Al. Their characteristics are investigated based on the model of Modified Qantum Molecular Dynamics (MQMD). Generally, the theoretical calculations are in good agreement with the experiment data. But in the forward angles the yield of the fragments is underestimated by MQMD model while in the case of the intermediate angle region, the calculation is higher than the experiment data in some degree for the fragments whose charge numbers are in the vicinity of the proiectile. The angular & charge distributions of the fragments are also compared with the statistical model of GEMINI. The results turn out to be that a small proportion of the statistical evaporation component exists in the forward angles while in the intermediate angle region, this component increases to some extent. However, its ratio is still small. It is found that the equilibrium evaporation component decreases gradually when the Z of the fragments becomes smaller.