Investigating the fission dynamics of the following neutron shell closed nuclei within a stochastic dynamical approach: 210Po, 212Rn, and 213Fr

TL;DR

This study demonstrates that a stochastic dynamical model can accurately reproduce experimental data on fission and related observables for neutron shell closed nuclei around mass 200 without additional shell or entrance channel effects, highlighting the model's robustness.

Contribution

The paper introduces a stochastic dynamical approach with a universal friction form factor that effectively describes fission data for shell closed nuclei, avoiding the need for extra effects or parameter adjustments.

Findings

Successfully reproduces experimental data for $^{210}$Po and $^{212}$Rn.

Achieves good agreement for their isotopes $^{206}$Po and $^{214,216}$Rn.

Identifies deviations in some Fr isotopes beyond experimental errors.

Abstract

Dissipative dynamics of nuclear fission is a well confirmed phenomenon described either by a Kramers-modified statistical model or by a dynamical model employing the Langevin equation. Though dynamical models as well as statistical models incorporating fission delay are found to explain the measured fission observables in many studies, it nonetheless shows conflicting results for shell closed nuclei in the mass region 200. Analysis of recent data for neutron shell closed nuclei in excitation energy range 40$-$80 MeV failed to arrive at a satisfactory description of the data and attributed the mismatch to shell effects and/or entrance channel effects, without reaching a definite conclusion. In the present work we show that a well established stochastic dynamical code simultaneously reproduces the available data of pre-scission neutron multiplicities, fission and evaporation residue excitation functions for neutron shell closed nuclei $^{210}$Po and $^{212}$Rn and their isotopes $^{206}$Po and $^{214,216}$Rn without the need for including any extra shell or entrance channel effects. The calculations are performed by using a phenomenological universal friction form factor with no ad-hoc adjustment of model parameters. However, we note significant deviation, beyond experimental errors, in some cases of Fr isotopes.