Neutron resonance parameters of bromine-79 and bromine-81.

Abstract

Neutron resonances of separated isotopes of bromine were measured using a TOF spectrometer of the Japan Atomic Energy Research Institute electron linear accelerator. Transmission and capture measurements were made with a 6Li-glass and a Moxon-Rae detector respectively, on separated isotopes (~98%) of 79Br and 81Br. Resonance analyses were made on transmission data with an area analysis code, and on capture data with a Monte-Carlo program. For 79Br gΓo/n values of 156 levels below 10 keV are obtained, and for 81Br 100 levels below 15 keV. The s-wave strength function So , average level spacing <D>, and average radiation width <Γr> are obtained; for 79Br So= (1.27 ± 0.14) 10−4 <D>=45±5eV, <Γr>= 293±20 meV, and for 81Rr So= (0.86±0.14) 10−4 <D> = 70±12eY, <Γ r> = 234±20 meV. For 79Br statistical properties of resonances are in good agreement with the predictions of the statistical model. Intermediate structures are observed in the resonances of 81Br showing clusters of levels at 1.2, 4.4, 10.0, 11.5 and 14.1 keV, where the curve of cumulative sum of gΓO/n vs. neutron energy shows steep rises.