Eur. Phys. J. A (2015) 51: 173
https://doi.org/10.1140/epja/i2015-15173-1

Regular Article - Theoretical Physics

A method to calculate fission-fragment yields Y(Z,N) versus proton and neutron number in the Brownian shape-motion model

Application to calculations of U and Pu charge yields

¹ Theoretical Division, Los Alamos National Laboratory, 87545, Los Alamos, NM, USA
² Yukawa Institute for Theoretical Physics, Kyoto University, 606-8502, Kyoto, Japan

^* e-mail: moller@lanl.gov

Received: 12 February 2015
Accepted: 26 May 2015
Published online: 23 December 2015

Abstract

We propose a method to calculate the two-dimensional (2D) fission-fragment yield versus both proton and neutron number, with inclusion of odd-even staggering effects in both variables. The approach is to use the Brownian shape-motion on a macroscopic-microscopic potential-energy surface which, for a particular compound system is calculated versus four shape variables: elongation (quadrupole moment Q₂), neck d , left nascent fragment spheroidal deformation , right nascent fragment deformation and two asymmetry variables, namely proton and neutron numbers in each of the two fragments. The extension of previous models 1) introduces a method to calculate this generalized potential-energy function and 2) allows the correlated transfer of nucleon pairs in one step, in addition to sequential transfer. In the previous version the potential energy was calculated as a function of Z and N of the compound system and its shape, including the asymmetry of the shape. We outline here how to generalize the model from the “compound-system” model to a model where the emerging fragment proton and neutron numbers also enter, over and above the compound system composition.