Impact of multichance fission on fragment-neutron correlations in ²²⁷Pa

We investigate the influence of neutron emission in the fission of Pa-227 populated by complete fusion of F-19 with Pb-208 at various excitation energies (E*). Mass gated pre-scission neutron multiplicities (.pre) were determined by fragment-neutron angular correlation and time of flight of fission fragments and neutrons using the National Array of Neutron Detectors facility. Obtained Mass - nu(pre) correlation showed that, at lower E* = 24.2 and 32.4 MeV, larger nu(pre) is correlated with asymmetric mass division. On the other hand, at higher E* = 46.1 and 59.6 MeV, larger nu(pr)e is correlated with symmetric mass division. The results were analyzed within the framework of the general description of fission observables GEneral description of Fission observables (GEF) model with multichance fission included. The analysis of fragment mass-total kinetic energy correlation for different chance fission clearly indicates a revival of shell effects at E* = 24.2 and 32.4 MeV as a consequence of sequential fission decay. At these energies, higher chance fission decreases the saddle point excitation energy considerably where shell effects are prominent. The interplay of shell mediated mass asymmetric fission and symmetric fission gives rise to an energy dependent Mass - nu(pre) correlation. We have compared the experimental results with Mass -nu(pre) correlation predicted by the GEF model. It is concluded that the correlation of larger nu(pre) with asymmetric mass at lower excitation energies is a signature of shell effects reinstated by sequential fission decay. At the two higher excitation energies, despite the multichance fission and consequent decrease in saddle point energy, the available excitation energy appears sufficient for the attenuation of shell effects.