Correlations of midrapidity light charged particles (LCPs) and intermediate mass fragments (IMFs) with projectile-like fragments (PLFs) have been examined from the 35 MeV/u ${}^{70}\mathrm{Zn}+{}^{70}$Zn, ${}^{64}\mathrm{Zn}+{}^{64}$Zn, and ${}^{64}\mathrm{Ni}+{}^{64}$Ni reaction systems. A new method was developed to examine the flow of the particles with respect to the PLF. The invariant PLF-scaled flow allowed for the dynamics of the midrapidity $Z=1–4$ particles to be studied. Strong differences in the PLF-scaled flow were observed between the different isotopes. In particular, the most $n$-rich LCPs exhibited a negative PLF-scaled flow in comparison to the other LCPs. A classical molecular dynamics model and a three-body Coulomb trajectory simulation were both used to show that the PLF-scaled flow observable could be connected to the average order of emission of the LCPs. The experimental results suggest that the midrapidity region is preferentially populated with neutron-rich LCPs and $Z=3–4$ IMFs at a relatively early stage in the collision. The deuteron and ${}^3$He particles are emitted later followed, lastly, by protons and alphas. The average order of emission of the midrapidity LCPs was extracted from the constrained molecular dynamics simulations and showed good agreement with the emission order suggested by the experimental PLF-scaled flow results.

• Received 16 August 2012

DOI:https://doi.org/10.1103/PhysRevC.86.044605