Source: http://www.journalchemistry.org/article/125/10.11648.j.sjc.20180604.15
Timestamp: 2019-04-20 09:08:29+00:00

Document:
A solid-state nuclear clock based on the low-lying isomeric state in 229Th 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, Thn+ n < 4 ions could open non-radiative decay routes for deexcitation, hindering the photon emission. Here we have used time-resolved photoluminescence (TRPL) and density functional theory (DFT) calculations to characterize MgF2 crystals that have been implanted with 229Th recoils via a-decay from a 233U source with the goal of determining the charge state of the implanted thorium atoms. The DFT calculations predicted Th4+ to be the lowest energy oxidation state with Th3+ the next lowest in the MgF2 crystal environment. The DFT calculations also show Th4+:MgF2 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 Thn+ n < 4 ions several orders of magnitude smaller than the number of implanted 229Th recoils. This work shows that the solid-state approach is a viable option for a nuclear clock.
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