摘要
In the framework of a modified Fisher model,using the isobaric yield ratio method,we investigate the fragments produced in the 140 A Me V 40,48Ca+9Be and 58,64Ni+9Be projectile fragmentation reactions.Using different approximation methods,asym/T (the ratio of symmetry-energy coefficient to temperature) of symmetric and neutron-rich fragments are extracted.It is found that asym/T of fragments depend on the reference nucleus and the neutron excess of fragments.The asym/T of the isobar decreases when the neutron-excess of the isobar increases,while for a fragment with the same neutron-excess,asym/T increases as the mass of the fragment increases but saturate when the mass of the fragment becomes larger.
基金
Supported by the National Natural Science Foundation of China under Grant No 10905017
the Program for Innovative Research Team(in Science and Technology)under Grant No 2010IRTSTHN002 in the Universities of Henan Province,and the Young Teacher Project in Henan Normal University.
