Cross sections for neutron capture from surrogate measurements: An examination of Weisskopf-Ewing and ratio approximations

TL;DR

This paper evaluates the accuracy of surrogate reaction methods for determining neutron capture cross sections, focusing on Weisskopf-Ewing and ratio approximations, and discusses potential improvements for deformed nuclei.

Contribution

It critically assesses the validity of common approximations in surrogate reactions and proposes directions for more accurate cross section extraction methods.

Findings

Weisskopf-Ewing approximation has limitations for deformed nuclei.

Ratio approximation improves accuracy but still has constraints.

Surrogate methods can estimate (n,gamma) cross sections within certain uncertainties.

Abstract

Motivated by the renewed interest in the surrogate nuclear reactions approach, an indirect method for determining compound-nuclear reaction cross sections, the prospects for determining (n, gamma) cross sections for deformed rare-earth and actinide nuclei are investigated. A nuclear-reaction model is employed to simulate physical quantities that are typically measured in surrogate experiments and used to assess the validity of the Weisskopf-Ewing and ratio approximations, which are typically employed in the analysis of surrogate reactions. The expected accuracy of (n,gamma) cross sections extracted from typical surrogate measurements is discussed and limitations of the approximate methods are illustrated. Suggestions for moving beyond presently-employed approximations are made.