热核三重碎裂和伴随粒子裂变的实验研究

THE STUDY BY EXPERIMENT ON THREEFOLD FRAGMENTATION OF SINGLE HOT NUCLEUS AND FISSION WITH COMPANION OF PARTICLES

对中能核反应中的三体碎裂数据的处理中对整体形变的真的三重碎裂与三体事件（如裂变加上类弹碎片或蒸发粒子）进行鉴别：这时对它们的质量谱、发射平面方向分布作了比较，再次证明了整体形变三重碎裂的确是存在的．伴随粒子裂变测量给出非全熔合裂变与周边碰撞的跟随裂变两种方式，它们的产额比与伴随粒子的探测角有关联．裂片出平面的幅角分布存在两组，分别与两种伴随粒子裂变相对应．周边碰撞跟随裂变的出平面的幅角为３８度．从非全熔合裂变的幅角分布的宽度可量度蒸发粒子数目从而得到复合核的激发能或核温度．非全熔合裂变的伴随粒子在大角度下为纯蒸发粒子，从纯蒸发粒子的能谱和测出的同位素比也可得到核温度．实验还测量了３０ＡＭｅＶ４０Ａｒ核弹在１５９Ｔｂ和ｎａｔ．Ａｇ靶子上的削碎的碎片，得到碎片的动量谱和其宽度．宽度为７５ＭｅＶ／ｃ，与期待值一致．在６度测出碎片产额是一样的，可是在９度测出的碎片愈重产额愈小．

The data of prompt threefold fragmentation (3F)of single hot nucleus with whole deformation emerged from three body events , such as fission followed projectile -like fragment (PLF)or particles evaporated (PE)from the hot nuclei. The identifications were made by a comparison of the mass spectrum and the orientation of emission plane. Again it is true that the 3F evidently exist. In fission with companion particles there are two modes, one is sequential fission (SF)with PLF and another is in-complete fusion-fission (ICF) with PE. The yield ratio of ICF over SF is dependent on the emission angle of these particles. Also the out-of-the reaction plane azimuth angle distributes two kind peaks: one at zero degree is associated with ICF in central collision and other at 38° with SF in peripheral collision. By the width of the zero degree peak the nuclear temperature can be extracted. Also at backward the light particles are nearly pure evaporated, with the isotope ratio and the energy spectrum the nuclear temperature can be obtained. The projectile of 40 Ar at 30 A MeV with target Tb and Ag breakup emission (PBE) has been measured . The momentum standard deviation of the fragment is 75 MeV/c that is expected. At 6° the PBE is isotopically against emission mass number of fragment, however at 9° the yield decreases with the mass number.