Ground state deformation parameters of 154Sm extracted from fusion barrier distribution

Abstract

Abstract

Abstract Heavy ion-induced fusion reactions, analysed within the coupled-channels framework, have been found to provide useful information about ground state deformation of the collision partners. We revisit the fusion reaction 16O+154Sm and examine the different coupling schemes in interpreting the measured fusion cross sections. Furthermore, we aim to extract ground state deformation parameters of the rare earth nucleus 154Sm. Fusion barrier distribution is derived from experimental fusion cross sections using an analytic recipe, which assumes the barrier to be a multi-Gaussian function. Different sets of deformation parameters of 154Sm, corresponding to different coupling schemes, are extracted by application of the chi-square (χ2) minimization technique. Bayesian analyses are performed for optimal estimation of uncertainties in the extracted values of quadrupole (β2), octupole (β3) and hexadecapole (β4) deformation parameters in each case. Employing the method of iNdependent Bayesian Model Averaging (NBMA), β2, β3 and β4 of 154Sm are determined to be 0.28 ± 0.06, 0.06 ± 0.06 and 0.09 ± 0.04, respectively. It is observed that the barrier distribution is more sensitive to minor changes in the inputs of the coupled-channels model, in contrast to the excitation function which remains largely unaffected by such changes. The methodology used in this work has been quite effective in determining the ground state deformation parameters of 154Sm. Similar strategy can be adopted to study the shape of other nuclei, by judicious choice of coupling schemes and careful application of the χ2-minimization technique.