Laser-Induced Quenching of the Th-229 Nuclear Clock Isomer in Calcium Fluoride

TL;DR

This study demonstrates laser-induced quenching in calcium fluoride to depump the Th-229 nuclear isomer, reducing its lifetime and potentially improving solid-state nuclear clock performance.

Contribution

It introduces laser-induced quenching as a novel method to control Th-229 isomer population in CaF2, addressing readout limitations in nuclear clocks.

Findings

Achieved threefold reduction in isomer lifetime

Demonstrated LIQ at wavelengths 148-420 nm

Effective at temperatures 100-350 K

Abstract

The 10-minute radiative lifetime of the first excited $^{229}$Th$^{4+}$ nuclear state in ionic crystals provides narrow spectroscopic linewidths, enabling the realization of a solid-state nuclear clock. Due to the 4+ noble gas configuration, electronic readout or state initialization schemes known from atomic clocks are inaccessible. This elongates the interrogation cycle, which will deteriorate the clock performance. To address this limitation we demonstrate laser-induced quenching (LIQ) as a method of depumping the $^{229}$Th isomer population in CaF$_2$. We provide experimental evidence for LIQ at different wavelengths (148 - 420 nm) and temperatures (100 - 350 K), achieving a threefold reduction in the isomer lifetime with 20 mW of laser power.