Neutron-Induced Cross Sections for Stable Selenium Isotopes (A = 74–82) Using the EMPIRE-3.2 Code with Coupled-Channels Optical Model Calculations

Abstract

A comprehensive theoretical evaluation of neutron-induced reaction cross sections 
for the stable selenium isotopes 74–82Se is presented using the EMPIRE-3.2 nuclear 
reaction modeling code. The global Koning–Delaroche optical model potential is 
adopted as the principal interaction framework and is augmented by coupled
channels calculations to explicitly account for vibrational collective excitations in 
the even-A isotopes. Pre-equilibrium emission processes are treated with advanced 
implementations of the DEGAS and PCROSS modules, enabling a realistic description 
of multi-step direct and compound mechanisms. Nuclear structure inputs are taken 
from the RIPL-3 database, including microscopic Hartree–Fock–BCS level densities 
and generalized Lorentzian γ-ray strength functions to ensure physically consistent 
statistical decay modeling. Calculations cover neutron energies from thermal values 
up to 30 MeV and include total, elastic and inelastic scattering, as well as (n,γ), (n,p), 
(n,2n), and (n,α) reaction channels. Local adjustments of optical model parameters, 
supported by systematic sensitivity analyses, are performed to optimize agreement 
with available experimental datasets from the EXFOR library. The results 
demonstrate excellent reproduction of measured (n,p) excitation functions in the 
10–20 MeV region and accurate prediction of (n,2n) reaction thresholds and peak 
cross sections. Compared with default TALYS outputs and evaluated nuclear data 
libraries ENDF/B-VIII.0 and JENDL-5, the EMPIRE-3.2 calculations show improved 
performance in pre-equilibrium-dominated channels, reducing discrepancies to 
approximately 10–20%. The refined cross sections provide improved input for 
modeling the weak s-process nucleosynthesis in massive stars, particularly at the 
branching points near ^79Se and ^80Se, and contribute to enhanced accuracy in 
reactor dosimetry and activation analyses. Overall, the study demonstrates the 
effectiveness of quantum-mechanical optical model approaches in bridging 
experimental data gaps for medium-mass nuclei.