> For the first time, it has been possible to use a laser to transfer an atomic nucleus into a state of higher energy and then precisely track its return to its original state.

We've known about photon-atom interactions for well over 100 years, with excitation of electrons which are either released or drop back to the original orbit, right?

So, ok, the Nucleus is smaller and the energies to alter the quantum state are probably higher, but - why is this so special, and why Thorium in particular rather than any old nuclei?

Disclaimer: I'm not a physicist.