自发双α衰变：首个实验极限与探测前景
Spontaneous double alpha decay: First experimental limit and prospects of investigation
AI总结：
本文探讨双α衰变可能性，基于现有数据首次设定209Bi半衰期下限为2.9e20年，理论估计约1e33年，认为实验探测前景悲观。
摘要：
对于多种核素，同时发射两个α粒子的核衰变在能量上是可能的。本文讨论了在元素天然同位素组成中存在的核素中寻找此类衰变的前景。利用文献[P. de Marcillac等人，Nature 422 (2003) 876]的数据，首次为209Bi的2α衰变设定了半衰期实验极限，即T1/2 > 2.9e20年（90%置信水平）。文中还给出了该过程的理论T1/2估计值。基于这些数值（约为1e33年或更长），可以得出结论：实验观测2α衰变的前景非常悲观。
英文摘要：
Nuclear decays with simultaneous emission of two alpha particles are energetically possible for a number of nuclides. Prospects of searching for such kind of decay for nuclides present in the natural isotopic composition of elements are discussed here. The first experimental limit on half-life for 2alpha decay is set for 209Bi as T1/2 > 2.9e20 y at 90% C.L., using the data of work [P. de Marcillac et al., Nature 422 (2003) 876]. Theoretical T1/2 estimations for the process are also given. Using these values, which are on the level of 1e33 y or more, one can conclude that the prospects of experimental observation of 2alpha decay are very pessimistic.
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