It is well known that the spontaneous emission rates of atoms or molecules can be modified by changing their electromagnetic environment, which is typically an optical cavity. But the same is hard to achieve for nuclear transitions because the frequency of the radiation emitted in most nuclear transitions is much larger than that of the cavity modes. Eugene Tkalya of Moscow State University now predicts that the decay rate via emission of 229Th from its lowest excited nuclear state can be increased or decreased by an order of magnitude by placing the atom in a dielectric sphere or a thin film. The effect could lead to ultraprecise atomic clocks based on nuclear transitions.

Further reading

E V Tkalya 2018 Phys. Rev. Lett. 120 122501.