High-precision frequency measurements of atomic transitions can be used to probe physics beyond the Standard Model and are bounded only by the ability to calculate nuclear and electronic effects. Precise isotope-shift  measurements of ground and low-lying atomic states depend heavily on a detailed description of the nuclear structure and are therefore very difficult to calculate theoretically. In contrast, Rydberg states (atomic states with high principal $n$ and angular $\ell$ quantum numbers) are less affected by nuclear and electronic systematics than low lying atomic states, mainly due to the large orbital radius of the valance electron and its negligible overlap with the nucleus.

This suggest Rydberg atoms as a good platform for searches of new physics, such as light force mediators between neutrons in the nucleus and electrons, as they are potentially able to disentangle the new physics observable from the unknown nuclear effects. This suggest Rydberg atoms as a good platform for searches of new physics, such as light force mediators between neutrons in the nucleus and electrons, as they are potentially able to disentangle the new physics observable from the unknown nuclear effects.