Description
Nowadays, the most precise clocks are atomic clocks. These devices use the transition of cesium (133Cs) atoms between two electronic states to control the frequency and they can measure time with an accuracy of 1 second within 300 million years. To improve this precision, scientists want to use the resonant transition between the ground and excited levels of the nuclei of long-lived isomers.
An international team of scientists from the United States and Europe, led by Yuri Shvyd’ko of Argonne National Laboratory (USA) and Tomasz Kołodziej of SOLARIS, successfully excited for the first time with X-rays an isomeric state in Scandium-45—the sharpest quantum transition in the hard X-ray regime.
European XFEL in the so-called self-seeding mode provided an X-ray beam with an appropriate spectral density to excite the desired resonance. At the MID beamline, 25-micrometer thick scandium foils were irradiated with an X-ray laser beam, and resonance was observed by the time-delayed emission of the characteristic Kα and Kβ radiation by scandium atoms. Using sophisticated noise reduction techniques and high-resolution X-ray optics, the resonant transition energy was determined with an unprecedented accuracy to 5 decimal places, (12.38959 keV). The width of the resonance is about a million times smaller than in the Mössbauer isotope of iron 57Fe (it still remains to be measured precisely in the further steps), which in turn gives a time measurement accuracy on the order of 1 s per 300 billion years, i.e. 1,000 times better than previously achieved in atomic clocks.
The resonant excitation of the scandium-45 isomer, together with the precise determination of the resonance energy (previously known only with an accuracy of +/-50 eV), opens up completely new possibilities for the construction of ultra-precise clocks (the so-called atomic nuclear clock), in spectroscopy and metrology with previously unattainable resolutions, and new measurements of basic physical quantities.
Reference:
Shvyd'ko, Y., Röhlsberger, R., Kocharovskaya, O., (…) & Kołodziej, T. “Resonant X-ray excitation of the nuclear clock isomer 45Sc”, Nature 622, 471–475 (2023)
