Direct detection of the 229Th nuclear clock transition
Direct detection of the 229Th nuclear clock transition
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DOI：
10.1038/nature17669
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发表时间：
2016-05-05
期刊：
影响因子：
64.8
通讯作者：
Thirolf, Peter G.
中科院分区：
文献类型：
--
作者：
von der Wense, Lars;Seiferle, Benedict;Thirolf, Peter G.
今天最精确的时间和频率测量是用光学原子钟进行的。然而，有人提出，它们可能会被核钟超越，核钟采用核跃迁而不是原子壳层跃迁。只有一种已知的原子核状态可以用现有技术作为原子核时钟，即Th-229的同分异构第一激发态（表示为Th-229 m）。在这里，我们报告的直接检测到这种核状态，这是进一步确认的异构体的存在，并奠定了基础，其衰变参数的精确研究。根据这种直接探测，同分异构体的能量被限制在6.3和18.3电子伏之间，并且发现Th-229 m（2+）的半衰期长于60秒。更精确的测定似乎是可以实现的，并将为制定核频率标准铺平道路。
Today's most precise time and frequency measurements are performed with optical atomic clocks. However, it has been proposed that they could potentially be outperformed by a nuclear clock, which employs a nuclear transition instead of an atomic shell transition. There is only one known nuclear state that could serve as a nuclear clock using currently available technology, namely, the isomeric first excited state of Th-229 (denoted Th-229m). Here we report the direct detection of this nuclear state, which is further confirmation of the existence of the isomer and lays the foundation for precise studies of its decay parameters. On the basis of this direct detection, the isomeric energy is constrained to between 6.3 and 18.3 electronvolts, and the half-life is found to be longer than 60 seconds for Th-229m(2+). More precise determinations appear to be within reach, and would pave the way to the development of a nuclear frequency standard.