In this paper we review results obtained in the searches of double beta decays to excited states of the daughter nuclei and illustrate the related experimental techniques. In particular, we describe in some detail the only two cases in which the transition has been observed; that is the $2{\beta }^{-}(0^{+}\to 0_1^{+})$ decay of ${}^{100}$Mo and ${}^{150}$Nd nuclides. Moreover, the most significant results in terms of lower limits on the half-life are also summarized.

中文翻译：

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双倍β衰变对子核兴奋态的影响

在本文中，我们回顾了从双β衰变搜索到子核激发态获得的结果，并说明了相关的实验技术。特别是，我们详细描述了仅观察到过渡的两种情况；那就是$2{\beta }^{-}（0^{+}\to 0_{\mathrm{1个}}^{+}）$ 的衰变 ${}^{100}$莫和 ${}^{150}$Nd核素。此外，还总结了降低半衰期的最显着结果。