Role of higher-multipole deformations in exotic C14 cluster radioactivity

Abstract

We have studied nine cases of spontaneous emission of C14 clusters in the ground-state decays of the same number of parent nuclei from the trans-lead region, specifically from Fr221 to Th226, using the preformed cluster model (PCM) of Gupta and collaborators, with choices of spherical, quadrupole deformation (β<inf>2</inf>) alone, and higher-multipole deformations (β<inf>2</inf>, β<inf>3</inf>, β<inf>4</inf>) with cold "compact" orientations θc of decay products. The calculated C14 cluster decay half-life times are found to be in nice agreement with experimental data only for the case of higher-multipole deformations (β<inf>2</inf>-β<inf>4</inf>) and θc orientations of cold elongated configurations. In other words, compared to our earlier study of clusters heavier than C14, where the inclusion of β<inf>2</inf> alone, with "optimum" orientations, was found to be enough to give the best comparison with data, here for C14 cluster decay the inclusion of higher-multipole deformations (up to hexadecapole), together with θc orientations, is found to be essential on the basis of the PCM. Interestingly, whereas both the penetration probability and assault frequency work simply as scaling factors, the preformation probability is strongly influenced by the order of multipole deformations and orientations of nuclei. The possible role of Q value and angular-momentum effects are also considered in reference to C14 cluster radioactivity. © 2011 American Physical Society.