[denton-scratch]

> clocks even better than those using transitions in the spectra of ions or neutral atoms

I'd be interested to know how much more accurate a nuclear-state-transition clock might be than a conventional Caesium or Rubidium clock.

TFA seems to make the point that a nuclear clock would be more resistant to external influences, such as EM radiation, than an atomic clock, and so could be used in experiments where such influences might introduce unwanted uncertainty. But I'd like to know what the claim for greater accuracy is based on, rather than simply greater reliability.

[wbl]

You have the math turned around. Because the nuclear resonance is much more stable and high frequency the Q factor and accuracy of the measurement is higher. With a cesium or rubidium clock it's very difficult to control all the influences on how tightly the nominal resonance is achieved and the Q while impressive is a bit less.

There are some real challenges in realization: this will take optical combs and all sorts of other stuff to really take advantage of.

[pfdietz]

They also point out that because the thorium atoms can be embedded in a solid, and have motion << the wavelength of the radiation, the emission and absorption are largely recoil-free. This eliminates Doppler broadening. What broadening there could be was below the resolution of their pump beam.