Neutron to proton ratios of quasiprojectile and midrapidity emission in the ${58}$Ni-${58}$Ni reaction at 52 MeV/Nucleon

By combining data from a charged particle $^{58}$Ni+$^{58}$Ni experiment at 52 MeV/nucleon with an $^{36}$Ar+$^{58}$Ni experiment at 50 MeV/nucleon for which free neutrons have been detected, an increase in the neutron to proton ratio of the whole nuclear material at midrapidity has been experimentally observed in the reaction $^{58}$Ni+$^{58}$Ni at 52 MeV/nucleon. The neutron-to-proton ratio of the quasi-projectile emission is analyzed for the same reactions and is seen to decrease below the ratio of the initial system. Those observations suggest that an asymmetric exchange of neutrons and protons between the quasiprojectile and the midrapidity region exists.