Microscopic pairing in fission dynamics

TL;DR

This paper demonstrates that including pairing correlations as dynamical degrees of freedom in a microscopic model significantly improves the accuracy of predicting spontaneous fission half-lives in fermium isotopes.

Contribution

It introduces a two-dimensional microscopic approach incorporating pairing correlations and deformation parameters to better model fission dynamics.

Findings

Pairing correlations are crucial for accurate fission half-life predictions.

Least-action paths differ from minimum-energy paths, emphasizing the role of pairing.

The method reproduces experimental half-lives in fermium isotopes.

Abstract

Nuclear fission can be modelled as a quantum tunneling process driven by the interplay between the nuclear binding energy and the collective inertia. Within the Wentzel-Kramers-Brillouin formalism, spontaneous fission half-lives can be obtained by minimizing the action integral in the multidimensional space of collective degrees of freedom. Hence, including the relevant collective variables is crucial for properly describing spontaneous fission probabilities. Pairing correlations play an essential role in this evaluation since the collective inertia decreases as the inverse of the square of the pairing gap, and, therefore, they should be considered as a relevant degree of freedom on the same footing as deformation parameters. In this work, we show that the spontaneous fission half-lives in fermium isotopes can be reproduced in a microscopic theory by considering the least-action fission path in a two-dimensional space with constraints on the quadrupole moment and pairing correlations. We consider two microscopic quantities as degrees of freedom associated with pairing: the pairing gap parameter $\Delta$, and the particle number fluctuations $\langle \Delta N^2 \rangle$. Least-action paths, computed using the Dijkstra algorithm, are compared with minimum-energy paths, highlighting the importance of pairing correlations as a dynamical degree of freedom.