2023-11-16 アルゴンヌ国立研究所(ANL)
◆スカンジウム-45の原子核をX線で励起し、極めて長寿命な核状態を利用して時計信号を生成。核時計は原子時計よりも安定性が高く、温度変化や電磁場の影響を受けにくい特性を持ちます。この成功はスカンジウム-45核時計の可能性を示し、今後はさらなる研究や高度なX線ソースの発展が期待されます。
＜関連情報＞
- https://www.anl.gov/article/scientists-move-closer-to-longtheorized-ultraprecise-nuclear-clock
- https://www.nature.com/articles/s41586-023-06491-w
核時計異性体45Scの共鳴X線励起に成功 Resonant X-ray excitation of the nuclear clock isomer 45Sc
Yuri Shvyd’ko,Ralf Röhlsberger,Olga Kocharovskaya,Jörg Evers,Gianluca Aldo Geloni,Peifan Liu,Deming Shu,Antonino Miceli,Brandon Stone,Willi Hippler,Berit Marx-Glowna,Ingo Uschmann,Robert Loetzsch,Olaf Leupold,Hans-Christian Wille,Ilya Sergeev,Miriam Gerharz,Xiwen Zhang,Christian Grech,Marc Guetg,Vitali Kocharyan,Naresh Kujala,Shan Liu,Weilun Qin,Alexey Zozulya,Jörg Hallmann,Ulrike Boesenberg,Wonhyuk Jo,Johannes Möller,Angel Rodriguez-Fernandez,Mohamed Youssef,Anders Madsen & Tomasz Kolodziej
Nature Published:27 September 2023
DOI:https://doi.org/10.1038/s41586-023-06491-w
Abstract
Resonant oscillators with stable frequencies and large quality factors help us to keep track of time with high precision. Examples range from quartz crystal oscillators in wristwatches to atomic oscillators in atomic clocks, which are, at present, our most precise time measurement devices1. The search for more stable and convenient reference oscillators is continuing2,3,4,5,6. Nuclear oscillators are better than atomic oscillators because of their naturally higher quality factors and higher resilience against external perturbations7,8,9. One of the most promising cases is an ultra-narrow nuclear resonance transition in 45Sc between the ground state and the 12.4-keV isomeric state with a long lifetime of 0.47 s (ref. 10). The scientific potential of 45Sc was realized long ago, but applications require 45Sc resonant excitation, which in turn requires accelerator-driven, high-brightness X-ray sources11 that have become available only recently. Here we report on resonant X-ray excitation of the 45Sc isomeric state by irradiation of Sc-metal foil with 12.4-keV photon pulses from a state-of-the-art X-ray free-electron laser and subsequent detection of nuclear decay products. Simultaneously, the transition energy was determined as 12,389.59±0.15(stat) +0.12(syst) eV with an uncertainty that is two orders of magnitude smaller than the previously known values. These advancements enable the application of this isomer in extreme metrology, nuclear clock technology, ultra-high-precision spectroscopy and similar applications.
