Symmetry effects for inelastic scattering to the second, unbound, state in 9BE (5/2ˉ, 2.43 Mev) in the fermionic system 9BE + 9BE

Abstract

Elastic scattering and inelastic excitation of the second, unbound, state 9Be (5/2ˉ, 2.43 MeV) for the identical-particle fermionic system 9Be + 9Be have been measured at the highest incident beam energy presently available ELab(9Be) = 25 MeV. A 9Be beam, produced by the General Ionex Corporation model 860C sputter ion-source, was accelerated by the EN Tandem Van de Graaff accelerator of the iThemba LABS (Gauteng) and was used to bombard a thin 9Be target. The experimental equipment associated with the C-line includes a high resolution ΔE-E gas-ionisation detector coupled to a small scattering chamber. Energy loss and residual energy signals were processed using a CAMAC-based plus OS/2 WIMPS2 data acquisition system running on an online computer. The ΔE-E plots were used to identify the reaction products and their kinematic energies, thereby determining the elastic and inelastic scattering cross-sections. The elastic and inelastic scattering data were analysed in terms of the optical model and Distorted Wave Born Approximation, respectively. Angular distribution data for the elastic scattering for 9Be + 9Be conformed well to the optical model predictions using an energy-independent optical model potential. Inelastic scattering cross-sections were determined up to θc.m.  135° and symmetry effects were investigated. As such, excitation of the second, unbound, state 9Be (5/2ˉ, 2.43 MeV) via a strong E2 one-step two-body interaction from the 9Be (3/2ˉ, g.s.) did not show effects due to symmetry in the entrance channel. These results were consistent with a previous study at ELab(9Be) = 16 MeV.