We study neutron-proton equilibration in dynamically deformed nuclear systems by investigating the correlations between the two largest fragments produced in collisions of 70 The extent of equilibration is investigated using the rotation angle as a clock for the equilibration. The initially dissimilar fragments converge exponentially with consistent rate constants across a wide variety of reaction partners and systems, indicating the equilibration follows first-order kinetics.
Previous work has quantified the degree of neutron-proton equilibration in heavy-ion nuclear collisions by observing the convergence of isospin observables (such as the isoscaling parameter α) to an expected value based on similar symmetric reaction systems. We present a new signature of equilibration: the convergence of the isospin asymmetry (as quantified by three isoscaling metrics) of two mirror asymmetric reaction systems towards each other rather than a pre-defined point. For the reactions of 35 MeV/u 64,70 Zn+ 64,70 Zn and 64 Zn, 64 Ni+ 64 Zn, 64 Ni the neutron-proton equilibration was found to be approximately 80%, and this result is compared directly to previous work.
Isoscaling parameters α and β have been explored as a function of breakup angle in binary excited projectile-like fragment decays produced in collisions of 70 Zn + 70 Zn and 64 Zn + 64 Zn at 35 MeV per nucleon. In this analysis, focus was placed on isoscaling the second heaviest fragment with 4 ≤ ZL ≤ 8 emitted from the excited projectile-like fragment in events that contained a heavy fragment with ZH ≥ 12. The breakup orientation θprox was defined as the angle between the heavy and light fragments' center of mass velocity and the fragment pairs' relative velocity. Breakups between 0 • < θprox ≤ 80 • have been shown to be dominated by dynamical contributions, while break-up angles of θprox > 100 • are predominantly statistical. Historically, isoscaling has often been understood and applied in a statistical context, assuming that the fragments are produced after statistical equilibrium is achieved. Studying isoscaling parameters as a function of θprox reveals the sensitivity of α and β to the mechanism of fragment production.
The traditional isoscaling technique has been used to analyze all isotopically identified particles from 70 Zn+ 70 Zn and 64 Zn+ 64 Zn collisions at 35 MeV/u. Two additional techniques, using an energy-averaged ratio and using the data present in the tail of energy spectra, are compared to the traditional method and show similar results. Isoscaling fit parameters α and β are found both globally and for each individual series of constant Z and N. The data are then split up between emitted fragments and projectile-like fragments. Isoscaling values for the two different types of fragments are shown to be different, emphasizing the importance of experimentally distinguishing between projectilelike fragments and emitted fragments in order to achieve accurate isoscaling parameters.
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