Resonances in low energy elastic scattering of ?-particles from28Si

Abstract

The elastic scattering of e-particles from 2sSi at incident energies between 5 and 12MeV (4.4 and 10.5MeV in the centre-of-mass system) was studied to ascertain whether quasimolecular states exist for the e+ 28Si system, as predicted in the literature in terms of a microscopic theory based on the generator coordinate method. Angular distributions were obtained for angles larger than 70 ~ in energy steps of 100keV. Analysis of the experimental data was performed by coherently adding specific resonances to an underlying optical model which describes the background portion of the direct elastic scattering amplitude. As is usual, it was furthermore assumed that the average compound elastic contribution adds incoherently to the total cross section. In spite of the presence of a resonance characterized by an angular momentum value of J =3 in the energy region, as required by theory, no evidence could be found for the existence of other resonances with the expected J-sequence. We conclude that our experiment and analysis do not support the predictions of the microscopic theory.

Evaluation of Non-Rutherford Alpha Elastic Scattering Cross-sections for Silicon

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