Isomers as a bridge between nuclear and atomic physics

The year 2021 marks exactly 100 years since Otto Hahn discovered the first example of nuclear isomerism. The existence of long-lived nuclear excited states opens a window on nuclear structure and applications. From isomers, the availability of electromagnetic decay pathways enables coupling to the atomic electrons, such that nuclear and atomic transitions become interdependent. The nuclear decay process of internal conversion is the most well known. However, observation of its inverse, nuclear excitation by free electron capture, is controversial and requires further research. In this work, the relationship between nuclear and atomic transitions is outlined, and examples are discussed of the use of external electromagnetic radiation to manipulate nuclear transitions associated with isomers. •Nuclear isomers offer opportunities for electromagnetic manipulation.•The long-lived Ta-180 isomer has been deexcited by 1 MeV photon irradiation.•Interactions with atomic electrons are key for low-energy isomer manipulation.•Nuclear excitation by free electron capture (NEEC) needs experimental confirmation.