Evaluation of Neutron Capture Gamma-ray Spectra for 89Y, 93Nb, 127I, 133Cs, 141Pr, 197Au, natTl, and 209Bi

Abstract

The neutron capture gamma-ray spectra for 8 nuclides, 89 Bi, were calculated by using the Hauser-Feshbach statistical model, and their results were compared with the available experimental data. Two dominant ingredients to perform the statistical calculation were the level densities described by the Gilbert-Cameron approach with an improved systematics, and the gamma-ray transmission coefficients described by gamma-ray strength functions. Although various gamma-ray strength functions with a Lorentzian formula have been developed by using the photonuclear data or a microscopic analysis, they have failed to reproduce the occasional anomalous bumps observed near or below a neutron binding. In this work, we could reproduce the bumps well by adding a Lorentzian with an energy-temperature dependent width into a giant electric dipole resonance with an enhanced generalized Lorentzian. In addition, we introduced a correction function so as to compensate for the shortcomings due to missing levels or level-cuts.

Evaluation of neutron nuclear data on iodine isotopes

“…In the present calculation, the shape was determined by comparing with the gamma-ray spectra measured by Voignier et al [32] at 500 keV. Three terms were needed to reproduce the spectra, i.e., a giant-dipole resonance (GDR), a pygmy resonance and a correction term, as in the analysis performed by Kim et al [33]. A generalised Lorentzian (GLO), which was proposed by Kopecky and Uhl [34], was used for the GDR and the pygmy resonance, while the correction term was based on a standard Lorentzian (SLO).…”