**Nuclear effect** The deformed shape of the ytterbium-173 nucleus (right) makes it possible to excite the clock transition with a relatively low-power laser. The same transition is forbidden (left) if the nucleus is not deformed. (Courtesy: Physikalisch-Technische Bundesanstalt (PTB)) An atomic transition in ytterbium-173 could be used to create an optical multi-ion clock that is both precise and stable. That is the conclusion of researchers in Germany and Thailand who have characterized a clock transition that is enhanced by the non-spherical shape of the ytterbium-173 nucleus. As well as applications in timekeeping, the transition could be used in quantum computing. Furthermore, the interplay between atomic and nuclear effects in the transition could provide insights into the physics of deformed nuclei. The ticking of an atomic clock is defined by the frequency of the electromagnetic radiation that is absorbed and emitted by a specific transition between atomic energy levels.…