Partition between the fission fragments of the excitation energy and of the neutron multiplicity at scission in low-energy fission

Abstract

The partition between the light ($L$) and the heavy ($H$) fission fragments of the excitation energy available at scission is studied in the framework of the sudden approximation, i.e., under the assumption that the neck rupture and the absorption of the neck pieces by the fragments happen infinitely fast. We are dealing with a sudden transition between two different nuclear configurations (${\ensuremath{\alpha}}_{i}\ensuremath{\rightarrow}{\ensuremath{\alpha}}_{f}$) and we only need to know the two sets of neutron eigenstates involved. The accent in the present work is put on the dependence of this share of energy on the mass asymmetry ${A}_{L}/{A}_{H}$ of the primary fission fragments during the low-energy fission of ${}^{236}$U. In particular, for every fragment mass $A$ we estimate the scission neutron multiplicity ${\ensuremath{\nu}}_{\mathrm{sc}}$, the average energy cost for their release $\ensuremath{\langle}{E}_{\ensuremath{\nu}\mathrm{sc}}\ensuremath{\rangle}$, the primary fragments' excitation energy ${E}_{\mathrm{sc}}^{*}$, and the corresponding temperature ${T}_{\mathrm{sc}}$. The results are analyzed separately for each value of $\ensuremath{\Omega}$ (the projection of the angular momentum on the symmetry axis). As general trends, a decrease of ${E}_{\mathrm{sc}}^{*}$ (${T}_{\mathrm{sc}}$) and an increase of ${\ensuremath{\nu}}_{\mathrm{sc}}$ ($\ensuremath{\langle}{E}_{\ensuremath{\nu}\mathrm{sc}}\ensuremath{\rangle}$) with increasing $A$ were observed.