Nuclear Two-Photon Decay of 72mGe with an Isochronous Heavy-Ion Storage RingONLINE ONLY

The nuclear two-photon (2γ) decay is a rare decay mode in atomic nuclei whereby a nucleus in an excited state emits two gamma rays simultaneously. First order processes usually dominate the decay, however two-photon emission may become significant when first order processes are forbidden or strongly retarded, which can be achieved at the experimental storage ring ESR (GSI/FAIR). Within this work we will present the implemented methodology and the obtained results of a beam time performed in 2021, when for the first time the isochronous mode of the ESR alongside two non destructive Schottky detectors were operated for the study of short-lived isomers. We investigated specifically the isotope 72Ge, as it is the most easily accessible nucleus having a first excited 0+ state below the pair creation threshold paramount for the study of 2γ decay without competition of first order decays.
Preliminary results point out that its half-life is considerably shorter than expected from the extrapolation of previously studied 0+ → 0+ transitions, most likely related to the different nuclear structure of this mid-shell nucleus as compared to the previously studied closed-shell nuclei. Therefore, new theoretical investigations are required which, in combination with our experimental measurements, will allow us to determine the nuclear polarizabilities. Our successful measurement at the ESR paves the way to further studies of exotic decay modes which in turn will facilitate our understanding of electron-shell-nucleus interactions.