Predictions for neutron-tagged Coulomb dissociation in ultraperipheral Ru+Ru and Zr+Zr collisions

The photonuclear response reflects nuclear structure and the dynamics of excitation and decay, with neutron-emission channels retaining information that can be obscured in inclusive dissociation yields. We calculate specified-side and mutual neutron-tagged Coulomb-dissociation cross sections in ultraperipheral ${}_{44}^{96}\mathrm{R}\mathrm{u}+{}_{44}^{96}\mathrm{R}\mathrm{u}$ and ${}_{40}^{96}\mathrm{Z}\mathrm{r}+{}_{40}^{96}\mathrm{Z}\mathrm{r}$ collisions at $\sqrt{s_{\mathrm{N}\mathrm{N}}}=200\mathrm{G}\mathrm{e}\mathrm{V}$ using an impact-parameter-dependent equivalent-photon framework with photonuclear inputs from TALYS calculations and ENDF evaluations. Across the two input sets, the predicted Ru/Zr ratios span $1.54$-$1.71$ for exact $1n$ and $2.49$-$3.09$ for $1n1n$, while inclusive $Xn$ (at least one neutron) and $XnXn$ ratios remain near unity at $0.96$-$0.99$ and $1.05$-$1.10$, respectively. The one-neutron ratios lie well above the corresponding flux-only $Z^2$ and $Z^4$ charge-scaling references, reflecting differences in the low-energy one-neutron response that are amplified by mutual tagging. This topology hierarchy identifies neutron-tagged isobar ratios as sensitive probes of photonuclear response, revealing response differences hidden in inclusive dissociation. These calculations also provide neutron-emission inputs for neutron-tagged vector-meson photoproduction in isobar collisions.