image: Pα values for the Po and Rn isotopic chains obtained from various models, including the present and previous results of the present group. A similar variation in all curves is clearly displayed. view more
Credit: ©Science China Press
Probing the preformation of the α-particle in the α-decay process is a very attractive subject in studies of nuclear structure. Recently, this crucial α-preformation probability was empirically deduced and exhibits a new feature that had been inferred to some extent by Professor REN Zhongzhou and his group from Department of Physics, Nanjing University. This work, titled "Model-independent trend of α-preformation probability", was published in SCIENCE CHINA Physics, Mechanics & Astronomy 2013, Vol. 56(8).
Dating back to the end of the 19th century, nuclear physics established itself as a field of science with the discovery of radioactivity. Since those years, α decay has always been considered the eminent topic in nuclear physics. In particular, as the dominant decay mode of superheavy nuclei, it is currently the only useful tool in the identification of any new heavy element and its isotopes. Theoretically, the decay process is usually imagined in the Gamow picture as a preformed α cluster tunneling through the α-daughter potential barrier. Without doubt, the α-preformation probability is critical in view of nuclear structure. Nevertheless, detailed studies of this quantity provide results that remain ambiguous, despite extensive experimental investigations.
In the present work, the authors proposed an empirical formula that for the first time directly deduces the preformation factor of the αparticle from the experimental data. The α-preformation factors of 171 even-even nuclei were initially obtained that strongly confirmed the key role played by the shell effect in the formation of the α cluster during decay. The study was also extended to include heavier cluster emissions with satisfactory results. These in turn prove to a certain degree that the present analysis of the α-preformation factor is reasonable and reliable.
Interestingly, a new feature of the α-preformation probability (Pα) became evident in a further study. From a different perspective, the α-preformation probabilities for a given isotopic chain extracted from different theoretical analyses were found to have quite similar behavior when comparing the present results with other studies. Across the various studies, the relative trend in the α-preformation probabilities for an isotopic chain were actually model-independent, although the deduced values of the α-preformation factor based on the respective model differ from each other (see Figure 1). The inference is that these studies are consistent with each other despite the different theoretical models, and the present study can be taken as a certain proof of reliability of the previous theoretical results.
This study gives valuable information on the preformation probability of emitted particles in α-decay, and the new model-independent feature has been identified in detail. The researchers hope that the present investigation can be extended to a broader range of nuclei, and be used to provide clues for their follow-up work on nuclear structure.
This research was supported by the National Natural Science Foundation of China (Grant Nos. 11035001, 10975072, 10735010 and 11120101005), the National Major State Basic Research and Development of China (Grant Nos. 2010CB327803 and 2013CB834400), the Knowledge Innovative Program of the Chinese Academy of Sciences (Grant No. KJCX2-SW-N02), the Research Fund of Doctoral Point (RFDP) (Grant No. 20100091110028), the Project Funded by the Priority Academic Programme Development of Jiangsu Higher Education Institutions (PAPD), the Research and Innovation Project for College Postgraduate of Jiangsu Province (Grant No. CXZZ12¬_0031) and the Science and Technology Development Fund of Macau (Grant No. 068/2011/A).
See the article: QIAN Y B, REN Z Z*. Model-independent trend of α-preformation probability. SCIENCE CHINA Physics, Mechanics & Astronomy, 2013, 56(8):1520-1524.
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