Isomeric cross sections for the (n, 2n) reaction on 82Se, 81Br, and 45Sc at 15.1 MeV

Abstract

Activation techniques have been used to measure the cross sections at 15.1 MeV neutron energy for the following reactions: 82Se(n, 2n) 81m+gSe, 81Br(n, 2n) 80m+gBr, and 45Sc(n, 2n) 44m+gSc. Isomeric cross-section ratios were evaluated by applying the method of least squares to the time behavior of γ-ray activity following the ground-state decay of each isomeric pair. The absolute cross section σ m for the formation of the metastable state was measured by the mixed-powder method with the 27Al(n, α) 24Na reaction as the monitor. The cross section σ g for the formation of the ground state was then determined by using the isomeric cross-section ratio. The sum of σ m and σ g for each reaction is compared with the theoretical value obtained from calculations based on the statistical model for the formation of a compound nucleus and its subsequent emission of neutrons.