Progress Towards a ²²⁹Th Solid-State Nuclear Clock

In the ²²⁹Th nucleus, there exists a low-energy isomeric clock state that is roughly 8.4 eV above the ground state. This isomeric state has potential applications in ultra-stable and accurate chronometry [1], probing solid state environments [2], and tests of fundamental physics [3]. Recently, laser excitation of the isomeric state has been achieved [4]. Since then, our group has focused on measurements and calculations that will aid in the development of these applications. This includes, but is not limited to, observation of a photoquenching process that may speed up clock interrogation cycles [5], theoretical analysis of more accurate and stable crystal host materials [6], and work towards laser excitation with a dual VUV frequency comb system.

[1] C. J. Campbell et al., "Single-Ion Nuclear Clock for Metrology at the 19th Decimal Place," Phys. Rev. Lett., 108, 120802 (2012). DOI: 10.1103/PhysRevLett.108.120802.

[2] P. Gütlich, C. Schröder, and V. Schünemann, “Mössbauer spectroscopy—an indispensable tool in solid state research,” Spectroscopy Europe/World 24, 21–31 (2012).

[3] W. G. Rellergert, D. DeMille, R. R. Greco, M. P. Hehlen, J. R. Torgerson, and E. R. Hudson, “Constraining the evolution of the fundamental constants with a solid-state optical frequency reference based on the 229Th nucleus,” Physical Review Letters. 104, 200802 (2010).

[4] R. Elwell, C. Schneider, J. Jeet, J. Terhune, H. Morgan, A. Alexandrova, H. Tan, A. Derevianko, and E. Hudson, Laser excitation of the 229Th nuclear isomeric transition in a solid-state host, Physical Review Letters 133, 10.1103/PhysRevLett.133.013201 (2024).

[5] J. E. S. Terhune et al., "Photo-Induced Quenching of the ²²⁹Th Isomer in a Solid-State Host," arXiv:2412.08998 [physics.atom-ph] (2024). [Online]. Available: https://arxiv.org/abs/2412.08998.

[6] H. W. T. Morgan, R. Elwell, J. E. S. Terhune, H. B. T. Tan, U. C. Perera, A. Derevianko, A. N. Alexandrova, and E. R. Hudson, 229Th-doped nonlinear optical crystals for compact solid-state clocks (2024).