Optical Transmission Enhancement of Ionic Crystals via Superionic Fluoride Transfer: Growing VUV-Transparent Radioactive Crystals

Abstract

The 8 eV first nuclear excited state in ${}^{229}$Th is a candidate for implementing an nuclear clock. Doping ${}^{229}$Th into ionic crystals such as CaF${}_2$ is expected to suppress non-radiative decay, enabling nuclear spectroscopy and the realization of a solid-state optical clock. Yet, the inherent radioactivity of ${}^{229}$Th prohibits the growth of high-quality single crystals with high ${}^{229}$Th concentration; radiolysis causes fluoride loss, increasing absorption at 8 eV. We overcome this roadblock by annealing ${}^{229}$Th doped CaF${}_2$ at 1250$\unicode{x2103}$ in CF${}_4$. The technique presented here allows to adjust the fluoride content without crystal melting, preserving its single-crystal structure. Superionic state annealing ensures rapid fluoride distribution, creating fully transparent and radiation-hard crystals. This approach enables control over the charge state of dopants which can be used in deep UV optics, laser crystals, scintillators, and nuclear clocks.

5 pages, 5 figures

References in corpus (4)

• Observation of the radiative decay of the ${}^{229}\mathrm{Th}$ nuclear clock isomer
• Performance of a 229 Thorium solid-state nuclear clock
• Nuclear clocks based on resonant excitation of gamma-transitions
• Sensitivity of Nuclear Transition Frequencies to Temporal Variation of the Fine Structure Constant or the Strong Interaction

Cited by in corpus (4)

• Frequency ratio of the ${}^{229\mathrm{m}}$Th nuclear isomeric transition and the ${}^{87}$Sr atomic clock
• ${}^{229}{\mathrm{ThF}}_4$ thin films for solid-state nuclear clocks
• Controlling ${}^{229}$Th isomeric state population in a VUV transparent crystal
• Probing New Forces with Nuclear Clocks