Presented by: Lars von der Wense, Ludwig-Maximilians-University of Munich

Abstract: A nuclear optical clock based on a single 229Th ion is expected to achieve a higher accuracy than the best atomic clocks operational today [1]. Although already proposed back in 2003 [2], such a nuclear frequency standard has not yet become reality. The main obstacle that has so far hindered the development of a nuclear clock is an imprecise knowledge of the energy value of a nuclear excited state of the 229Th nucleus, generally known as the 229Th isomer. This metastable nuclear excited state is the one of lowest energy in the whole nuclear landscape and - with an energy of less than 10 eV - offers the potential for nuclear laser spectroscopy, which poses a central requirement for the development of a nuclear clock. In the past few years significant progress toward the development of a nuclear frequency standard has been made: Starting with a first direct detection of the 229Th isomer in 2016 based on its internal conversion decay channel [3], the isomeric lifetime could be determined in 2017 [4], followed by a first laser-spectroscopic characterization in 2018 [5]. Most recently, a first energy determination based on the isomer’s direct detection was successful [6]. This new knowledge provides, in combination with an achieved drastically enhancement of XUV-frequency comb intensity [7], the basis for improved efforts toward the laser-based search for the nuclear transition [8, 9], which can ultimately lead to the development of a nuclear optical clock. In this presentation I will give an overview over the current status of the nuclear clock development, with a particular focus on the most recent progress. Also the next required steps will be detailed and future perspectives will be given.
References
[1] C.J. Campbell et al., Phys. Rev. Lett. 108, 120802 (2012).
[2] E. Peik and C. Tamm, Eur. Phys. Lett. 61, 181 (2003).
[3] L. von der Wense et al., Nature 533, 47 (2016).
[4] B. Seiferle et al., Phys. Rev. Lett. 118, 042501 (2017).
[5] J. Thielking et al., Nature 556, 321 (2018).
[6] B. Seiferle et al., Nature 573, 243 (2019).
[7] G. Porat et al., Nature Photonics 12, 387 (2018).
[8] L. von der Wense, Phys. Rev. Lett. 119, 132503 (2017).
[9] L. von der Wense and C. Zhang, arXiv:1905.08060 (2019).

Host: Jun Ye

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