Optimum orientation versus orientation averaging description of cluster radioactivity

TL;DR

This study compares the decay descriptions of heavy nuclei in both optimum orientation and orientation-averaged models, revealing significant differences in decay widths and preformation probabilities, emphasizing the importance of averaging over orientations for deformed nuclei.

Contribution

It introduces a detailed comparison between orientation-averaged and optimum orientation models in cluster radioactivity, highlighting the importance of averaging for deformed nuclei.

Findings

Orientation-averaged decay width is 1-2 orders of magnitude less than at optimum orientation.

Preformation probabilities increase when using the averaged decay width.

Results suggest averaging over orientations better accounts for nuclear deformations.

Abstract

Background: The deformation of the nuclei involved in the cluster decay of heavy nuclei affect seriously their half-lives against the decay. Purpose: We investigate the description of the different decay stages in both the optimum orientation and the orientation-averaged pictures of the cluster decay process. Method: We consider the decays of 232,233,234U and 236,238Pu isotopes. The quantum mechanical knocking frequency and penetration probability based on the Wentzel-Kramers-Brillouin approximation are used to find the decay width. Results: We found that the orientation-averaged decay width is one or two orders of magnitude less than its value along the non-compact optimum orientation. The difference between the two values increases with decreasing the mass number of the emitted cluster. Correspondingly, the extracted preformation probability based on the averaged decay width increases with the same orders of magnitude compared to its value obtained considering the optimum orientation. The cluster preformation probabilities (Sc) obtained in the two considered schemes give more or less comparable agreement with the Blendowske-Walliser (BW) formula based on the preformation probability of Sa(ave.) obtained from the orientation-averaging scheme. All the obtained results, including those obtained in the optimum-orientation scheme, deviate substantially from the BW law based on Sa(opt.) obtained using the optimum-orientation scheme. Conclusion: In order to account for deformations of the participating nuclei, it is more relevant to calculate the decay width by averaging over the different possible orientations of the participating deformed nucleus, rather than considering the corresponding non-compact optimum orientation.