The determination of hexadecapole deformation parameters in actinide nuclei and their variation near the nuclear surface

Abstract

By computing self consistently the nuclear density of 23SU with the Skyrme SIII effective force, the hexadecapole deformation parameter has been found to vary considerably in the nuclear surface. This suggests an explanation for some discrepancies observed between/34 parameters estimated from different inelastic scattering experiments.The precise determination of the shape of a nucleus remains a very difficult problem. This is particularly true for the determination of the nuclear deformation, a specific property of the shape of nuclei, which constitutes an outstanding task. A standard technique for investigating nuclear shapes and therefore nuclear deformation is the measurement of inelastic cross sections as was first suggested by R.C. Barrett [i].Indeed analysis of inelastic cross-sections by means of the deformed optical model potential (DOMP) in the coupled-channel formalism has been proved to be a powerful tool for the determination of multipole moments, in particular Y4 moments, of the equilibrium shape in rare earth nuclei [2]. More recent inelastic scattering experiments with protons [3], alpha particles [4], or polarized protons [5], analyzed through the DOMP indicated also the presence of large /34 terms in the shape of several 2s-ld nuclei. Although the existence of a I14 term in the shape of nuclei in the actinide deformed region has been predicted or estimated since a long time from analysis of alpha-decay rates [6], it is only recently that high resolution experiments have yielded reliable informations on/34 deformation in this region. Moreover precise experimental determination of nuclear deformation are timely, since many HartreeFock calculations of nuclear shapes in the actinide region have recently appeared in the litterature [7].

Analysis of scattering and reactions of aligned7Li-nuclei in a double folding model

“…However, the nuclear part of the projectile target interaction is not as well known as the Coulomb part and the strong absorption prohibits to obtain information on the inner part of the mass distribution of the interacting nuclei. This prevents the extraction of mass deformation parameters from experimental data without the use of model prescriptions to define the shape of the mass distributions and to connect them with the projectile target interaction [11]. Up to now several phenomenologically defined models have been applied for this purpose.…”