title: First nuclear two-photon decay measurements at storage rings
creator: Freire Fernández, David
subject: ddc-530
subject: 530 Physics
description: This thesis introduces a pioneering approach by combining Schottky and Isochronous Mass Spectrometry (S+IMS) to directly measure the nuclear two-photon or double-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 mass resolving power of 9.1 × 105 for IMS. This capability allowed us to successfully resolve excited states, down to the 101 keV isomer in 72 Br. 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 a significant 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 future research at storage rings.
date: 2024
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/35046/1/DavidFreireFernandez_thesis-pdfa.pdf
identifier: DOI:10.11588/heidok.00035046
identifier: urn:nbn:de:bsz:16-heidok-350460
identifier:   Freire Fernández, David  (2024) First nuclear two-photon decay measurements at storage rings.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/35046/
rights: info:eu-repo/semantics/openAccess
rights: Please see front page of the work (Sorry, Dublin Core plugin does not recognise license id)
language: eng