Energy of the 229Th nuclear clock transition
Energy of the 229Th nuclear clock transition
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DOI：
10.1038/s41586-019-1533-4
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发表时间：
2019-09-12
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：
Seiferle, Benedict;von der Wense, Lars;Thirolf, Peter G.
由于其低激发能量和长辐射寿命，钍-229的第一激发异构态Th-229 m可以通过激光进行光学控制（1，2），并且是创建核光学钟的理想候选者（3），预计将补充并优于当前基于电子壳层的原子钟（4）。核钟将有各种各样的应用，例如在相对论大地测量学（5），暗物质研究（6）和基本常数的潜在时间变化的观测（7），但它的发展迄今为止一直受到Th-229 m能量的不精确知识的阻碍。在这里，我们报告了一个直接测量的过渡能量的这种异构状态的基态的不确定性为0.17电子伏（一个标准偏差）使用光谱学的内部转换电子发射在飞行中的中性Th-229 m原子的衰变过程中。基态和第一激发态之间的跃迁能量对应于149.7 +/- 3.1纳米的波长，这是通过高次谐波产生的激光光谱学可获得的。我们的方法结合了核物理和原子物理测量，以推进精密计量，我们的研究结果有望促进高分辨率激光光谱在原子核上的应用，并使核光学时钟的发展具有前所未有的准确性。
Owing to its low excitation energy and long radiative lifetime, the first excited isomeric state of thorium-229, Th-229m, can be optically controlled by a laser(1,2) and is an ideal candidate for the creation of a nuclear optical clock(3), which is expected to complement and outperform current electronic-shell-based atomic clocks(4). A nuclear clock will have various applications-such as in relativistic geodesy(5), dark matter research(6) and the observation of potential temporal variations of fundamental constants(7)-but its development has so far been impeded by the imprecise knowledge of the energy of Th-229m. Here we report a direct measurement of the transition energy of this isomeric state to the ground state with an uncertainty of 0.17 electronvolts (one standard deviation) using spectroscopy of the internal conversion electrons emitted in flight during the decay of neutral Th-229m atoms. The energy of the transition between the ground state and the first excited state corresponds to a wavelength of 149.7 +/- 3.1 nanometres, which is accessible by laser spectroscopy through high-harmonic generation. Our method combines nuclear and atomic physics measurements to advance precision metrology, and our findings are expected to facilitate the application of high-resolution laser spectroscopy on nuclei and to enable the development of a nuclear optical clock of unprecedented accuracy.