STUDY OF THE N-Z RATIOS OF LIGHT AND HEAVY FRAGMENTS FROM COLLISIONS OF XE-129, XE-132 AND XE-136 WITH AU-197 NEAR THE INTERACTION BARRIER

The reactions of 761 MeV 129Xe ions, 764 MeV 132Xe ions and 787 MeV 136Xe ions with thick 197Au targets were investigated with radiochemical techniques. From the relative shift of the N/Z ratios observed with the different Xe projectiles a characteristic time of the order of 10-22 sec is estimated for the complete relaxation of the charge asymmetry mode. The most probable N/Z ratios deviate considerably from the N/Zratio of the composite system. Apparently, in the mass diffusion process a continuous readjustment of 〈N/Z〉 values takes place which minimizes the potential energy of the two separating fragments. The inclusion of shell corrections at low excitation energies and corrections for the breaking of nucleon pairs in the transfer process are shown to be essential in the potential energy calculations. These results, together with evidence for small widths in the N/Z distributions indicate strong correlations between proton and neutron exchanges in the damped collision process. © 1979.