Any of three processes of radioactive disintegration in which a Beta particle is spontaneously emitted by an unstable atomic nucleus in order to dissipate excess energy .

某些 不 稳定原子 核为耗散其过剩能量而自发发射一个β粒子的三种放射性衰变过程的统称。

Radioactive series : Any of four sets of unstable heavy atomic nuclei that undergo a series of alpha decay and Beta decay until a stable nucleus is achieved .

放射性系：四组 不 稳定的重原子核，通过一系列α衰变和β衰变直至达到稳定的 核为止。