Speaker
Description
$^{229}$Th has the lowest-energy first excited nuclear state of all known isotopes, corresponding to a wavelength of about 148.3 nm [1], which allows the nuclear transition to be studied and characterized using laser spectroscopy in the Vacuum Ultraviolet range. This property makes $^{229}$Th ideally suited for the development of nuclear clocks. Unlike atomic clocks, which use electronic transitions as a frequency reference, nuclear clocks are based on nuclear transitions [2]. Since nuclear transitions are inherently robust against external fields and the chemical environment [3], [4], they can provide greater stability and accuracy than electronic transitions. The lifetime of an excited nuclear state is influenced by the
charge state of the ion through the interaction with the surrounding electrons. By measuring the same nuclear transition for different charge states, it is possible to determine which charge state offers the
best conditions to build a nuclear clock, such as linewidth and magnetic field sensitivity.
Here we present the production of various highly charged $^{229}$Th ions using an electron beam ion trap (EBIT). The EBIT consists of a cathode, three drift tubes, a repeller, and an electron collector. The electron beam is generated by the cathode and is further radially confined by a longitudinal magnetic field. The electrostatic potential is generated by appropriately selecting the voltages applied to the drift tubes. After passing through the drift tubes, the electron beam is redirected by a repeller toward the collector. To load the EBIT with $^{229}$Th, the ions are extracted from a plasma plume generated from a $^{229}$Th target via laser ablation and transported directly into the EBIT. There, the ions are
trapped in the potential and are gradually ionized to higher charge states by the electron beam. Using a Wien filter detector, the produced ionic charge state distribution can be characterized.
In the future, by performing nuclear laser spectroscopy on $^{229}$Th highly charged ions, the most suitable ion for a nuclear clock can be found by careful characterization. Additionally, recent theoretical proposals highlight interesting prospects for nuclear spectroscopy of highly charged ions: the simultaneous self-consistent determination of all nuclear moments (magnetic-dipole and electric-quadrupole) and investigations into nuclear hyperfine mixing [5], where the nucleus and its electrons become fully entangled.
[1] J. Tiedau et al., PRL., vol. 132, no. 18, 2024.
[2] S. V. Pineda et al., arXiv: 2408.12309 [nucl-ex], 2024.
[3] W. G. Rellergertet al., PRL., vol. 104, no. 20,
2010.
[4] G. Kazakov et al., New Journal of physics,
vol. 14, no. 8, 2012.
[5] H. - Y. Zheng et al., arXiv:2606.15180, 2026.
| Academic level | Master's Student |
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