Vapour-deposited thin films raise the possibility of portable nuclear clocks

A rare isotope, thorium-229, exhibits a unique low-energy nuclear transition that could form the basis of a precise nuclear clock. Observation of this transition in vapour-deposited thin films, which require only minuscule amounts of 229Th, opens up a possible route to the widespread use of portable nuclear clocks. An innovative strategy could make portable nuclear clocks viable.