arXiv:2404.12311physics.atom-ph
Laser excitation of the $^{229}$Th nuclear isomeric transition in a solid-state host
Abstract
LiSrAlF$_6$ crystals doped with $^{229}$Th are used in a laser-based search for the nuclear isomeric transition. Two spectroscopic features near the nuclear transition energy are observed. The first is a broad excitation feature that produces red-shifted fluorescence that decays with a timescale of a few seconds. The second is a narrow, laser-linewidth-limited spectral feature at $148.38219(4)_{\textrm{stat}}(20)_{\textrm{sys}}$ nm ($2020407.3(5)_{\textrm{stat}}(30)_{\textrm{sys}}$ GHz) that decays with a lifetime of $568(13)_{\textrm{stat}}(20)_{\textrm{sys}}$ s. This feature is assigned to the excitation of the $^{229}$Th nuclear isomeric state, whose energy is found to be $8.355733(2)_{\textrm{stat}}(10)_{\textrm{sys}}$ eV in $^{229}$Th:\thor:LiSrAlF$_6$.
Here's the open-access arXiv preprint: https://arxiv.org/abs/2404.12311 ("Laser excitation of the ²²⁹Th nuclear isomeric transition in a solid-state host") Here's an HN thread with 215 additional comments, from two months ago: https://news.ycombinator.com/item?id=40194636…
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