Timescale for equilibration of N/Z gradients in dinuclear systems

TL;DR

This study investigates the timescale and factors influencing the equilibration of neutron-to-proton ratios in dinuclear systems formed during peripheral nuclear collisions, revealing a dependence on initial neutron gradients and target composition.

Contribution

It provides the first detailed measurement of N/Z equilibration timescales in transiently deformed projectile-like fragments, highlighting the role of initial conditions and target dependence.

Findings

N/Z equilibration persists for 3-4 zs after collision.

Neutron-rich fragments are associated with smaller rotation angles.

Target composition influences initial N/Z ratios.

Abstract

Equilibration of N/Z in binary breakup of an excited and transiently deformed projectile-like fragment (PLF*), produced in peripheral collisions of 64Zn + 27Al, 64Zn, 209Bi at E/A = 45 MeV, is examined. The composition of emitted light fragments (3<=Z<=6) changes with the decay angle of the PLF*. The most neutron-rich fragments observed are associated with a small rotation angle. A clear target dependence is observed with the largest initial N/Z correlated with the heavy, neutron-rich target. Using the rotation angle as a clock, we deduce that N/Z equilibration persists for times as long as 3-4 zs (1zs = 1 x 10^-21 s = 300 fm/c). The rate of N/Z equilibration is found to depend on the initial neutron gradient within the PLF*.