Isospin effect on products of nuclear fragmentation

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.