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Abstract:
This thesis introduces a pioneering approach by combining Schottky and Isochronous Mass Spectrometry (S+IMS) to directly measure the nuclear two-photonordouble-gamma (2γ) decay rate in the low-energy regime, below the electron-positron pair creation threshold. This method extends non-destructive lifetime spectroscopy to include shorter-lived species (≳ 1 ms), and achieves an unprecedented massresolving power of 9.1 × 105 for IMS. This capability allowed us to successfully resolve excited states, down to the 101 keV isomer in 72Br. We determined the half-life for the 2γ decay of the first-excited 0+ state in bare 72Ge ions to be 23.9 (6) ms, a finding that significantly diverges from prior expectations. This divergence potentially results from the structure of this mid-shell nucleus in comparison to the structures of the so far measured semi-magic and doubly-magic nuclei. Further investigations are required to fully understand these discrepancies. Furthermore, this work presents some of the most precise mass measurements ever achieved at storage rings. We notably improved the mass uncertainty for 69As and identified as ignificant deviation(> 3σ) for 72As from previously tabulated values. These results demonstrate the potential of our technique for mass measurements and for exploring nuclear decay pathways previously inaccessible, opening new venues for futurere search at storage rings.
