报告题目：Revision of potential description of alpha-decay and alpha-capture, new quasi-bound states and Gamow's puzzle 

　　报告人：Sergei P. Maydanyuk 研究员（乌克兰核物理研究所） 

　　时间安排：2017年6月6日15：00         

　　地点：近代物理所5号楼911会议室 

　　We analyze a current status of alpha decay and capture of alpha-particles by nuclei. In 1928, Gamow proposed an idea applied for description of alpha decay of nuclei [1], based on tunneling phenomena thought potential barrier and internal oscillations of the alpha-particle inside internal well of interaction potential before decay. These two physical processes were studied independently and they put key-points in modern determination of half-life for nuclear decays. Gamow didn't know how to describe these two processes in unified way. 

　　Starting from that time, many other ingredients describing structure of decaying nuclei and formation of the alpha cluster were added to theory. But, up to last days, there is no unified formalism which provides unified description of tunneling and internal oscillating processes of alpha-cluster mentioned above. Now experimental half-lives for about 340 decaying nuclei are described by this theory, and about 1240 nuclei are predicted on such a basis [2, 3]. Such information is in databases of National Nuclear Data Center (Brookhaven Nat. Lab., USA), Int. Atomic Energy Agency (IAEA, Viena; RIPL-2 database) [4]. However, according to our analysis, if to describe tunneling and internal oscillating processes in unified way, then half-lives estimated theoretically can be changed up to 200 times. 

　　We introduce new formalism for the alpha-decay and alpha-capture which resolves the problem above [5]. We give answer of the Gamow’s question how tunneling phenomenon and oscillations are connected in unified way in the studied reactions. One can obtain more clear understanding about these processes from inverse reaction which is capture of alpha-particle by nuclei. Some of results from such research are: 

　　1. Solution of this task requires to take into account new additional independent parameters, which were never considered, but have essential influence of results. One such parameter describes space distribution of wave function of the the alpha cluster inside nuclear region. This parameter characterizes dynamics of decay or capture (i.e. initial or final condition). It was absent even in simplest Gamow’s formula of half-live of decay in textbooks. 

　　2. We discover new most stable states of a compound nucleus (CN) formed during capture of alpha particle by nucleus. We call them as quasibound states and introduce them to quantum mechanics. With a simple example, we explain why these states cannot appear in traditional calculations of the alpha capture cross-sections based on monotonous penetrabilities of a barrier, but they appear in complete description of evolution of CN. We predict such states and determine fusion probabilities for the alpha-capture reactions alpha +40 Ca and alpha +44 Ca. 

　　3. Our method decreases error by 41.72 times for alpha +40 Ca and 34.06 times for alpha +44 Ca in a description of experimental data in comparison with existing results of other researchers. 

　　We analyze difference between our approach and theory of quasi-stationary states with complex energies applied for the alpha capture. We show that (1) that theory does not provide calculations for cross-section of the alpha capture (according to modern models of the alpha capture), in contrast to our formalism, (2) these two approaches describe different states of the alpha capture (for the same alpha-nucleus potential). 

　　[1] G. Gamow, Zur Quantentheorie des Atomkernes, Z. Phys. 51, 204 (1928). 

　　[2] V. Yu. Denisov, A. A. Khudenko, Atom. Data Nucl. Data Tables 95, 815 (2009). 

　　[3] B. Buck, et al., Atom. Data Nucl. Data Tables 54, 53 (1993); Y. A. Akovali, Nucl. Data Sheets 84, 1 (1998); S. B. Duarte, et al., Atom. Data Nucl. Data Tables 80, 235 (2002); G. Audi, et al., Nucl. Phys. A 729, 3 (2003); N. Dasgupta-Schubert, et al., Atom. Data Nucl. Data Tables 93, 907 (2007); I. Silisteanu, A. I. Budaca, Atom. Data Nucl. Data Tables 98, 1096 (2012); R. G. Lovas, et al., Phys. Rep. 294, 265 (1998); C. Xu, Z. Ren, et al., Phys. Rev. C93, 011306(R) (2016); R. Id Betan, W. Nazarewicz, Phys. Rev. C 86, 034338 (2012); D. S. Delion, R. J. Liotta, Phys. Rev. C 87 (4), 041302(R) (2013). 

　　[4] http://www.nndc.bnl.gov, http://www-nds.iaea.org. 

　　[5] S. P. Maydanyuk, P.-M. Zhang, S. V. Belchikov, Nucl. Phys. A 940, 89 (2015); S. P. Maydanyuk, P.-M. Zhang, L.-P. Zou, Phys. Rev. C (2017) | in press.