Tracking saddle-to-scission dynamics using N/Z in projectile breakup reactions

Fragments produced in binary splits of an excited projectile-like fragment (PLF${}^{*}$) formed in the reactions ${}^{124}$Xe $+$ ${}^{112,124}$Sn at an incident energy of 50 MeV/$A$ are examined. The dependence of the isotopic composition of light fragments ($4\ensuremath{\leqslant}{Z}_{L}\ensuremath{\leqslant}8$) on rotation angle allows one to explore changes in $N/Z$ on the time scale of the rotational period of the PLF${}^{*}$. Changes in the $N/Z$ of the fragments persist for times as long as 2--3 zs (600--900 fm/$c$). The two-component nature of the time dependence of $\ensuremath{\langle}N\ensuremath{\rangle}/Z$ for ${Z}_{L}=4$ and the $Z$ dependence are related to differences in the initial configurations and subsequent decay of the PLF${}^{*}$.