Excitation energy as a basic variable to control nuclear disassembly

Thermodynamical features of Xe system is investigated as functions of tempe rature and freeze-out density in the frame of lattice gas model. The calcul ation shows different temperature dependence of physical observables at dif ferent freeze-out density. In this case, the critical temperature when the phase transition takes place depends on the freeze-out density. However, a unique critical excitation energy reveals regardless of freeze-out density when the excitation energy is used as a variable instead of temperature. Mo reover, the different behavior of other physical observables with temperatu re due to different pf vanishes when excitation energy replaces temperature . It indicates that the excitation energy can be seen as a more basic quant ity to control nuclear disassembly.