The dependences of He and intermediate mass fragments (IMF) production rates in the reactions 55 MeV/u ^40Ar+^58,64 Ni on the isospin, impact parameter and primary excitation energy of the reaction nuclear system were studied by using the 4π charged particle multi-detector array system (MUDAL). For the mentioned two reaction systems, the measured He particle contribution in the total charged particle multiplicity increases with increasing the total charged particle multiplicity but for the contribution of IMFs in the total charged particle multiplicity increases with increasing the total charged particle multiplicity at lower total charged particle multiplicities, and latter on it drops down with further increasing of the total charged particle multiplicities (see Fig.l). The experimental results of these two reaction systems with the same nuclear charge indicate that the contribution of He and IMFs in the total charged particle multiplicities are obviously isospin dependent.
Hu Rongjiang, Wu Heyu, Jin Genming, Zhu Yongtai, Duan Limin Xiao Zhigang and Wang Hongwei
