Browsing by Author "Perez, Sandro M"

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    Alpha decay and alpha elastic scattering by heavy nuclei
    (1993) Tripe, Peter; Perez, Sandro M
    A simple three parameter cluster model has previously been developed by Buck, Merchant and Perez to successfully describe alpha decay half lives for more than 400 nuclei. An important feature of this model is that it envisages preformed (preformation factor, P=1.0) alpha particles in the parent nuclei to be moving in orbits with a large value of a global quantum number, G. The discontinuity in decay half-lives at the N=l26 neutron shell closure is then naturally explained by an increase of G as the alpha particle is forced into a higher orbit by the shell closure. We consider alternative approaches to this model and extend it to consider different values of P, and different changes in G at shell closures. We find the original approach of Buck et al., a radius fit with ΔG=2, is still the most successful, but that a potential fit with ΔG=4 turns out to be competitive, lending support to the suggestion that the proton shell closure is also felt. We have also analysed low energy (24.7MeV) scattering of alpha particles from a number of heavy nuclei in an attempt to find a common set of potential parameters that adequately reproduces both the decay and scattering data. Although not completely successful in this attempt, we find that the potential parameters obtained in the decay calculations provide a good first guess at the scattering potential parameters. The above analysis constrains P to the range 0.01≤P≤0.1, with the value of P=1.0 not ruled out.
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    Cluster model investigation of nuclear spectra and electric quadrupole transitions
    (2003) McBride, Vanessa A; Perez, Sandro M
    We review a cluster model for even-even nuclei and derive a new relation between the excitation energies and the electric quadrupole transition strengths of these nuclei. A novel method for determining the likely clustercore decompositions of a given nucleus is described, and is tested by comparing theoretical cluster model spectra with their experimental counterparts for a representative set of Yb isotopes. A further method, based on least squares fits to spectra, is also examined.
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    Cluster model studies of nuclei in the actinide region
    (2006) Seals, H E; Perez, Sandro M
    Three independent techniques for obtaining core-cluster partitions of nuclei in the actinide region are found to give consistent results. As a by-product the techniques generate theoretical decay constants and energy spectra in good agreement with their experimental counterparts. The relationship implied by the binary cluster model between core-cluster charge products and electric quadrupole transition strengths is confirmed; and a basis from which to extract quantitative information from Casten's correlations is introduced.