25MeV/u40Ar+115In反应中前中角区碎片发射研究

从25MeV/u⁴⁰Ar+¹¹⁵In反应前中角区出射碎片的能谱、角分布和Z电荷分布出发，讨论了碎片发射机制随出射角和核电荷数Z的渐进变化;用改进的量子分子动力学(MQMD)模型研究了碎片角分布及Z电荷分布,理论计算和实验值整体上符合较好,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,理论计算比实验值偏高；碎片产物的角分布及Z电荷分布还与统计模型GEMINI进行了比较,发现在前角区平衡蒸发的成分所占比例很小,中角区所占的比例有所增加,但仍然 关键词：

STUDIES OF FRAGMENT EMISSIONS AT FORWARD AND INTERMEDIATE ANGLES IN 25MeV/u40Ar+115In REACTION

On the basis of the energy spectra, the angular and Z distributions of the fragments emitted at forward and intermediate angle region in 25MeV/u ⁴⁰Ar+¹¹⁵In reaction, the evolution of emission mechanisms of fragments with the emission angles of the fragments in the laboratory system and the charge numbers of the fragments is discussed. The model of modified quantum molecular dynamics(MQMD) is employed to investigate the angular and Z distributions of the fragments. The theoretical calculations are in good agreement with the experimental data in general. 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 calculated result is higher than the experimental data for the fragments whose charge numbers are in the vicinity of the projectile. The angular and charge distributions of the fragments are also compared with the statistical model of GEMINI. It is found that a small proportion of the statistical evaporation component exists in the forward angle region while in the intermediate angle region, this statistical evaporation component shows a little increase. With the decrease of the fragment charge number, the non-equilibrium intermediate-velocity component goes up step by step and plays a leading role while the equilibrium evaporation one diminishes gradually.