Observing the Ping-pong Modality of Isospin Degree of Freedom in Cluster Emission from Heavy Ion Reactions

Abstract

Two-body correlations of the isotope-resolved light and heavy clusters are measured in ${}^{86}$Kr+${}^{208}$Pb reactions at 25 MeV/u. The yield and kinetic variables of the $A=3$ isobars, triton and ${}^3$He, are analyzed in coincidence with the heavy clusters of $7\le A\le 14$ emitted at the earlier chance. While the velocity spectra of both triton and ${}^3$He exhibit scaling behavior over the type of the heavy clusters, the yield ratios of $\mathrm{t}{/}^3\mathrm{He}$ correlate reversely to the neutron-to-proton ratio $N/Z$ of the latter, showing the ping-pong modality of the $N/Z$ of emitted clusters. The commonality that the $N/Z$ of the residues keeps the initial system value is extended to the cluster emission in heavy ion reactions. The comparison of transport model calculations to the data is discussed.