UBC Theses and Dissertations
On alpha-decay in heavy nuclei Scherk, Leonard Raymond
The alpha-particle reduced widths for the ground state in Po²¹² are calculated on the basis of the nuclear shell model, employing the technique of Harada, but treating the nuclear surface in a more direct manner. It is contended that the calculations of previous authors, who have generally used a square-edge nucleus and a Coulomb barrier rounded-off by the nuclear potential of Igo, have, essentially, used the equivalent square-edge nucleus model of Vogt. Their J.W.K.B. estimate of the barrier penetrabilities is checked by an analytic calculation in Chapter 3 and is found to be reasonable. It is shown in Chapter 4 that, in the scattering of an alpha-particle from the ground state of Pb²⁰⁸, the diffuse nuclear edge considerably enhances the one-body reduced widths and, in a direct manner, that it similarly enhances the one-body differential elastic scattering cross-section. In this manner, it is demonstrated that the radius involved in the equivalent square-edge nucleus model must be considerably larger than that of the diffuse-edge nucleus to which it corresponds. This is shown directly in Chapter 5, where the validity of the equivalent square-edge nucleus model in heavy nuclei is examined. It is contended that this explains the large radii found in previous calculations. This is demonstrated directly by repeating the calculation of Harada with the diffuse nuclear edge being introduced in a direct manner. Although the effects of configuration mixing have not been directly examined, it has been concluded that shell model calculations can explain the major part of rates provided that the nuclear surface is manner.
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