Steffen ChristensenNuclear clock just dropped, possibly improving time measurement by as much as six orders of magnitude.
Huge huge news.
Preprint of full article is at https://arxiv.org/abs/2404.12311
Laser excitation of the $^{229}$Th nuclear isomeric transition in a solid-state host
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$_6$.
Nice covering article in Physics: https://physics.aps.org/articles/v17/s75
"We also observe a narrow, laser-line width limited spectral feature at 148.38219(4)stat(20)sys nm,
which decays with a lifetime of 568(13)stat(20)sys s. This
feature does not appear in a 232Th-doped LiSrAlF6 crystal."
...7+ digits of precision on the wavelength means that this nuclear transition line is **rock**-stable.
Holy hell.