Breakthrough in Nuclear Clock research featured on title page of 'Nature'
05.09.2024
A breakthrough towards the realization of a Nuclear Clock based on the Thorium Isomer 229mTh was achieved in laser spectroscopy experiments performed at the Joint Institute for Laboratory Astrophysics (JILA) in Boulder (Colorado, USA) by the team of Prof. Jun Ye in an international collaboration with teams from TU Vienna (Austria), University of Mainz (Germany), École Polytechnique Fédérale de Lausanne (EPFL), Lausanne (Switzerland) and LMU Munich (Germany). The excitation of the low-energy (ca. 8.4 eV) thorium isomer was realized by irradiating a strongly 229Th doped CaF2 crystal (provided by TU Vienna) with narrowband (bandwidth ca. 300 kHz) laser light at around 148 nm from a vacuum ultraviolet (VUV) frequency comb laser. The nuclear resonance was excited and the electric quadrupole splitting could be resolved. The resonance frequency was directly linked and compared to a high-precision 87Sr optical atomic clock operated by the group of Prof. Ye. The frequency ratio between the 229Th nuclear clock transition and the 87Sr atomic clock was determined as v(Th)/v(Sr)= 4.707072615078(5) and thus to 12 digits precision! This breakthrough marks the demonstration of a first prototype of a nuclear clock. In the last 5 years the precision of the nuclear clock transition has been improved by 11 orders of magnitiude.
The corresponding publication was featured on the titlepage of the September 5 edition of 'Nature':
Chuankun Zhang, Tian Ooi, Jacob S. Higgins, Jack F. Doyle, Lars von der Wense, Kjeld Beeks, Adrian Leitner, Georgy A. Kazakov, Peng Li, Peter G. Thirolf, Thorsten Schumm & Jun Ye: Frequency ratio of the 229mTh nuclear isomeric transition and the 87Sr atomic clock, Nature 633, 63 (2024).