BARRIER DISTRIBUTION OF QUASI-ELASTIC BACKWAD SCATTERING IN VERY HEAVY REACTION SYSTEMS

Abstract

We have measured quasi-elastic backward scattering in the reactions of 48 Ti , 54 Cr , 56 Fe , 64 Ni , 70 Zn , 76 Ge and 86 Kr + 208 Pb to study the nucleus-nucleus interaction in Pb -based cold fusion. The barrier distributions were obtained from the first derivative of the measured excitation functions of quasi-elastic scattering cross sections normalized to the Rutherford scattering cross sections. The centroids of the barrier distributions showed deviations from several predicted barrier heights toward the low energy side except for the Christensen-Winther potential and the Aküz-Winther potential. The shapes of the barrier distributions were well reproduced by the results of a coupled-channel calculation taking account of the coupling effects of multi-phonon excitations of the quadrupole vibration for the projectiles and of the octupole vibration for the 208 Pb target. The present barrier distributions were also well reproduced by a semiclassical calculation taking into account the couplings of transfer channels and single-phonon excitations in the projectiles and the target.