A Laser Built for Nuclear Timekeeping

This is cool, because among the hurdles for a Th-229 clock is the difficulty in generating enough light for the transition.

“For most nuclear transitions, the energy difference between the two states lies in the kilo-electron-volt to mega-electron-volt range. Consequently, such transitions are inaccessible to today’s high-precision lasers, which can deliver photons of typically a few electron volts in energy. A long-known exception is the transition between the ground state and first excited state of thorium-229 nuclei. Indirect measurements over the past 50 years have gradually pinned down that transition’s energy difference to only about 8.4 eV. As a result, this transition is being actively investigated as a candidate for developing a nuclear clock.”

https://physics.aps.org/articles/v19/19

There’s a bit of boilerplate cheerleading in this, like it’s a press release. Any improvement to GPS a tenuous claim unless you’re talking about a pretty long horizon, and any suggestion of a portable frequency standard relies on the portability of the laser and not just the container for the atoms.