Isospin diffusion in semi-peripheral ${}^{58}Ni$ + ${}^{197}Au$ collisions at intermediate energies (I): Experimental results

Isospin diffusion in semi-peripheral collisions is probed as a function of the dissipated energy by studying two systems ${}^{58}Ni$ + ${}^{58}Ni$ and ${}^{58}Ni$ + ${}^{197}Au$, over the incident energy range 52-74\AM. A close examination of the multiplicities of light products in the forward part of phase space clearly shows an influence of the isospin of the target on the neutron richness of these products. A progressive isospin diffusion is observed when collisions become more central, in connection with the interaction time.