Oxidation State of &amp;lt;sup&amp;gt;229&amp;lt;/sup&amp;gt;Th Recoils Implanted into MgF&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; Crystals

Beau J Barker

doi:10.11648/j.sjc.20180604.15

Abstract

A solid-state nuclear clock based on the low-lying isomeric state in 229 Th has attracted growing interest. One potential problem for the solid-state nuclear clock approach is the suitability of the doped environment for photon emission of the nuclear isomeric state. Specifically, Th n+ n 2 crystals that have been implanted with 229 Th recoils via a-decay from a 233 U source with the goal of determining the charge state of the implanted thorium atoms. The DFT calculations predicted Th 4+ to be the lowest energy oxidation state with Th 3+ the next lowest in the MgF 2 crystal environment. The DFT calculations also show Th 4+ :MgF 2 system has a band gap large enough so that the internal electron conversion decay channel is suppressed. Experimentally, we found no evidence for thorium in oxidations state other than +4 using TRPL spectroscopy that has a detection limit for Th n+ n 229 Th recoils. This work shows that the solid-state approach is a viable option for a nuclear clock.

Highlights

The 229Th nucleus has an extremely low-lying excited nuclear state [1, 2]
Four separate systems were chosen to study the possible ways in which thorium atoms might embed in a host MgF2 crystal
We collected timeresolved photoluminescence (TRPL) spectra from three types of MgF2 plates: those exposed to 229Th recoils and αparticles, those exposed to only α-particles and unexposed MgF2 plates

Summary

Introduction

The 229Th nucleus has an extremely low-lying excited nuclear (isomeric) state [1, 2]. This energy is within the range of current laser technology, making direct excitation of the isomeric state possible and could lead to a new type of nuclear clock with a predicted quality factor of Q = f/∆f ≈1019 outperforming the current state-of-the-art atomic clocks [3,4,5] Such a clock could have a number of applications, such as the potential to test temporal variations of fundamental constants [6, 7], the realization of a γ-ray laser [8], and the possibility of more accurate navigation systems. A recent gas phase study by Wense et al was able to directly observe the deexcitation of the isomeric state, but not accurately measure its energy [12]

Methods

Results

Conclusion