Speaker
Description
Frequencies are the physical quantity that can be measured with highest precision with applications ranging from clock transitions over search for dark matter to high precision measurements and tests of fundamental constants. Currently, the most precise clock transitions are optical transitions [1]. However, there are also a few nuclear transitions featuring Q-factors on a similar level or even exceeding those of current optical clock transitions. While it may be more challenging to excite these nuclear transitions, they are less sensitive to environmental perturbations caused by electric or magnetic fields. Hence, the interest in nuclear clock transitions, especially Mössbauer transitions, has grown over the last years. Besides $^{229}$Th with its comparably low transition energy of ~8eV [2], one of the most promising candidates for a nuclear clock is the Mössbauer isotope $^{45}$Sc, which has a transition energy of 12.4keV and a natural lifetime of 460ms featuring a Q-factor of ~10$^{19}$. Because of these extreme properties, a direct excitation, which is necessary for applications, only recently became feasible with the advent of high-rep-rate hard x-ray self-seeded free electron lasers. Especially the pulse structure of European XFEL ideally matches the lifetime of the transition. Here, we report on the resonant x-ray excitation of the $^{45}$Sc isomeric state [3]. Our measurements were able to decrease the uncertainty of the transition energy to sub-eV level, which is two orders of magnitude smaller than previously known.
This research is supported in part by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract DE-AC02-06CH11357 and by the National Science Foundation grant No. PHY-2012194.
[1] A. D. Ludlow et al., “Optical atomic clocks”, Rev. Mod. Phys. 87, 637 (2015)
[2] B. Seiferle et al., “Energy of the 229Th nuclear clock transition”, Quantum Sci. Technol.
6, 034002 (2021).
[3] Y. Shvyd’ko et al., “Resonant X-ray excitation of the nuclear clock isomer 45Sc”,
submitted (2023)
