From Superfluid Coherence to High-$K$ Fragment Channels at Nuclear Scission

Abstract: The origin of fission-fragment spin remains unresolved. For $<sup>{236}$U fission, we combine deformation-dependent finite-temperature pairing with a multidimensional scission-spectrum analysis. Near the pairing-quenching boundary, pair breaking exposes near-Fermi high-$Ω$ intruder orbitals and opens high-$K$ channels. The resulting maximum spectroscopic capacities range from a few to more than a dozen units of $\hbar$. Rapid neck rupture acts as a non-adiabatic projection freeze-out, where pairing serves as a dynamical gate: its critical attenuation does not generate angular momentum but allows existing high-$K$ projections to be retained diabatically as local fragment-$K$ components while total angular momentum remains conserved.