Background: α decay remains one of the most fundamental decay modes in heavy nuclei, and its study provides crucial insights into nuclear structure, shell effects, and deformation properties. Plutonium isotopes, situated in a transitional region of the actinide chain, serve as an important testing ground for understanding the interplay between shell closures and deformation effects on decay dynamics.

Purpose: The present work aims to provide a comprehensive microscopic investigation of ground-state α-decay properties of plutonium nuclei within the preformed cluster-decay model (PCM), with a focus on identifying the structural factors that govern decay half-lives and their systematics across the isotopic chain.

Methods: Our analysis encompasses 24 isotopes of plutonium ($Z$ = 94) with mass numbers ranging from $A$ = 220 to $A$ = 244. Using the Proximity 1988 nuclear potential and optimizing the neck-length parameter, we aim to enhance predictive precision. The Wentzel-Kramers-Brillouin approximation is employed to compute the penetration probability, a critical factor in determining α-decay half-lives. The study extracts and analyses several essential decay parameters: barrier height ($V_B$), barrier position ($R_B$), preformation probability ($P_0$), and penetration probability ($P$), linking them to underlying nuclear structure features.

Results: The accuracy of the model is first verified by comparing predictions with experimentally known α emitters. Excellent agreement is observed for a broad range of isotopes, namely, ${}^{220-230,236,238-240,242,244}\mathrm{Pu}, {}^{216-219,221-228,230,232,233,235,236,238}\mathrm{U}, {}^{212-230,232}\mathrm{Th}, {}^{209-211,214-224,226}\mathrm{Ra}$, and ${}^{210,212-220,222}\mathrm{Rn}$. This confirms the robustness and applicability of the PCM approach in modeling α-decay phenomena. The study extends beyond known α emitters to offer theoretical predictions for isotopes lacking experimental confirmation. Notable candidates for future experimental observation due to strong theoretical signatures for ${}^{231,232,234}\mathrm{Pu}, {}^{220,234}\mathrm{U}, {}^{208,212}\mathrm{Ra}$, and ${}^{204-209,211}\mathrm{Rn}$. These predictions broaden the PCM utility in identifying promising α emitters in less-explored regions. Furthermore, certain nuclei show significant hindrance to α decay, likely due to unfavorable barriers or structural conditions, such as ${}^{233,235,237,241,243}\mathrm{Pu}, {}^{229,231,237,239,240}\mathrm{U}, {}^{231,233-236}\mathrm{Th}, {}^{213,225,227-232}\mathrm{Ra}$, and ${}^{221,223-228}\mathrm{Rn}$, which are predicted to be poor α emitters. In addition to these, we revealed crucial structural correlations for both $P_0$ and $P$, showing marked enhancement at $N=128$ parent nuclei, indicating highly favorable conditions for α decay, underscoring the dominant role of shell closures in α-decay dynamics. In addition to the well-established spherical magic number $N=126$, our study also identifies signatures of enhanced stability at new neutron numbers, notably $N=134$ and $N=144$ for Pu, $N=144$ for U, $N=124$ for Ra, and $N=122$ for Rn, suggesting the emergence of deformed shell closures in these regions. And also, plutonium isotopes exhibit significant deformation, which strongly affects barrier characteristics and decay rates, which is less pronounced for lighter actinide chains. To further validate our approach, we computed the standard deviation between the calculated α-decay half-lives and the available theoretical as well as experimental data, providing a quantitative measure of the model's accuracy.

Conclusions: This study reinforces the PCM framework as a powerful tool for understanding α-decay mechanisms from a microscopic perspective. The model successfully reproduces experimental systematics and extends predictive capabilities to nuclei lacking experimental data. The significant influence of shell closures, particularly at $N=126$ daughter nuclei, and the role of nuclear deformation are central to explaining observed decay behaviors. Plutonium isotopes serve as critical test cases for examining shell evolution and structural transitions, situated in a region where α decay begins to compete with alternative decay modes.

Close

PrevNext

View figure in article

• Alpha decay
• Binding energy & masses
• Cluster models
• Lifetimes & widths
• Nuclear binding
• Nuclear decay
• Nuclear shapes and moments
• Nuclear structure & decays
• Shell model
• A ≥ 220