Evidence of 'slow' relaxation of isospin degree of freedom

摘要

Isotope ratios, as a function of kinetic energy in units of MeV/u of outgoing particles, are analyzed at 20degrees in the reaction of Ar-40 + Sn-112,Sn-124 and 5degrees in Ar-36 + Sn-112,Sn-124 at incident energy of 35 MeV/u. Relative yield ratios to stable isotopes increase with kinetic energy for the isotopes with low N/Z ratio but decrease for those with high N/Z ratio. This different behavior shows evidence of isospin non-equilibrium in dissipative projectile emission processes. It is demonstrated that the time of isospin relaxation is shorter as or comparable with that of energy relaxation in these reactions. Double isotope-ratio temperature parameters, extracted in the Ar-36 induced reaction from projectile-like fragments, also support the non-equilibrium of isospin or/and temperature degrees of freedom. (C) 2002 Elsevier Science B.V. All rights reserved. References: 17