$\beta$-Delayed Neutron and Fission Calculations with Relativistic QRPA and Statistical Model

TL;DR

This paper develops a theoretical database for -delayed neutron emission and fission rates using relativistic QRPA and statistical models, aiding r-process nucleosynthesis simulations.

Contribution

It introduces a new microscopic approach combining relativistic QRPA and statistical models to predict -delayed neutron and fission rates for nuclei relevant to the r-process.

Findings

Calculated -delayed neutron branching ratios agree well with experimental data.

-delayed neutron emission significantly affects neutron drip line nuclei.

Fission branching ratios depend strongly on fission barrier data.

Abstract

A role of \beta-delayed neutron emission and fission in r-process nucleosynthesis attracts a high interest. Although the number of study on them covering r-process nuclei is increasing recently, uncertainties of \beta-delayed neutron and fission are still large for r-process simulations. Our purpose is to make a new database on \beta-delayed neutron emission and fission rates. To this end, the data that are not investigated experimentally have to be predicted. Microscopic theoretical approaches based on a nuclear energy density functional and statistical models are one of the competent tools for the prediction. To obtain \beta strength function, p-n relativistic QRPA is adopted. Particle evaporations and fission from nuclear highly excited states are estimated by the Hauser-Feshbach statistical model. \beta-delayed neutron branching ratios (P_n) are calculated and compared with experimental data. \beta-delayed fission branching ratio (P_f) are also assessed by using four different fission barrier data. Calculated P_n values are in a good agreement with experimental data. It is found that energy withdrawal by \beta-delayed neutron emission sensitively varies P_n values for nuclei near the neutron drip line. P_f are sensitively dependent on fission barrier data. Newly calculated data on \beta-delayed neutron emission and fission are summarized as a table in supplement material. They are provided for studies of r-process as well as other fields such as nuclear engineering.