Absolute cross-sections and excitation functions for α particles induced reactions on bromine between 10 and 24 MeV

Abstract

Absolute cross-sections and excitation functions for α induced reactions have been measured, from 10 to 24 MeV, by activation and stacked foil techniques. The following reactions were seen: Br 79(α, n)Rb 82 6.3 h, Br 79(α, αn)Br 78 6.4 min, Br 79(α, 2n)Rb 81 31.5 min and 4.7 h, Br 81(α, αn)Br 80 18 min and 4.4 h, Br 81(α, n)Rb 84 23 min. The experimental results have been compared with theoretical predictions based on optical model and statistical analysis. It seems that the magnitude of the cross-sections is best predicted by optical model calculations. The shape of the excitation function for compound nucleus formation agrees best with the continuum theory, but the shapes of the individual cross-sections are not in agreement with evaporation calculations and some of the excitation functions are very peaked. Isomeric ratios seem to indicate that the (α, αn) reactions proceed through direct interaction and that there might be some admixture of compound nucleus and direct reaction on the high energy side of (α, 2n) reactions.