Study On The Temperature Of Intermediate Mass Fragments In Heavy-ion Reactions

Inheavy-ion collision, temperature ?T? is one of the key questions. Since the nuclear system experiences evolution which changing with a very high temperature to a very lowone to form the final fragments, the study of temperature is very important.In this paper, the study includes two parts mostly.In the first part, we present an improved temrmometer (T_IB) for the intermediate-mass fragments. The improved thermometer is proposed based on the difference between the isobaric yield ratios ?IYRs?. In the thermometer, the residual free energy of the three isobars is replaced by that of the binding energy. We study and analyse the 1404 MeV ^40,48Ca + 9Be ?181Ta? and ^58,64Ni + 9Be?181Ta? projectile fragmentation reactions, the IA GeV ^124,136Xe + Pb projectile fragmentation reactions and the 1A GeV ^112,124Sn + ^112,124Sn reactions, and obtain the temperature of intermediate-mass fragments which are from the reactions. The results shows that: TheT_IB from most of the fragments in the ^40,48Ca and ^58,64Ni reactions is in the range of 0.6 MeV to 3.5 MeV and the T_IB from most of the fragments in the 1²⁴Xe ? ^112,124Sn reactions is in the range of 0.5 MeV to 2.5 MeV, while the range is 0.5 MeV to 4.0 MeV from most of the fragments in the 136Xe reactions. In general, formost of the fragments,T_IB in the ^40,48Ca and ^58,64Ni reactions are very similar ?except in the very neutron-richfragments?, and T_IBfrom intermediate-mass fragments in the ^124,136Xe and ^112,124Sn reactions is also similar.In the investigated reactions, T_IBfrom most of the intermediate-mass fragments is low.In the second part, we study the relation of temperature and A. An A-dependent temperature has been found both for the primary fragments and for the measured fragments in an improved isobaric-yield-ratio-difference method, which obeys the function T = 1/[C?1-k · A?] ,with C and k being parameters.The A-dependence of temperature can also be explained by the A-dependence of the difference between the free energy or binding energy among isobars.Within the finite temperature range, the A-dependence of the difference among the free energy andbinding energy is found to depend on A in the form of y = 1/[C?1 -k· A?] .For the measured fragment, the temperature obtained by the improved isobaric-yield-ratio-differencemethod depends on A in the manner of T = 1/[C?1-k·A?] within T?4MeV.For the measured fragment, the A-dependence of temperature can be explained by theA-dependence of the isobaric difference among free energy in a natural way.