The accurate prediction of rare isotopes produced in in-flight fission of a heavy nucleus is a key question to search for new neutron-rich isotopes in the new generation of radioactive ion beam factories. Assuming that the empirical $Q_g$ scaling discovered in the projectile fragmentation reaction is obeyed in fissile fragments, i.e., the cross section of the isotopic fragment exponentially depends on its $Q_g$ value, we studied the systematic behavior of fragments produced in the in-flight fission reactions of ${}^{238}\mathrm{U}$ measured at RIKEN and GSI. The results show that $Q_g$ of the fissile fragment adheres to the same systematic regularity. This mechanistic universality establishes the $Q_g$-scaling method as a unified framework for predicting fragment yields across the projectile fragmentation reactions and fission reactions, providing crucial guidance for experiments searching for rare nuclei near the neutron-drip line and the nuclear structural evolution. Furthermore, using $Q_g$ values derived from the AME2020 atomic mass evaluation, the systematic behavior demonstrates robustness and allows the extraction of mass excesses from newly measured cross sections of neutron-rich isotopes. The mass excesses for 13 new isotopes, that is, ${}^{89}\mathrm{Ga}, {}^{91,92}\mathrm{Ge}, {}^{93-95}\mathrm{As}, {}^{96,97}\mathrm{Se}, {}^{99-101}\mathrm{Ge}$, and ${}^{102,103}\mathrm{Kr}$, were determined via the $Q_g$ systematics, showing consistency with the well-known mass models.

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• Binding energy & masses
• Fission
• Heavy-ion reaction mechanisms
• Nuclear reactions
• A ≥ 220
• Nuclear data analysis & compilation