Kaufmann, Simon (2019)
Laser spectroscopy of nickel isotopes with a new data acquisition system at ISOLDE.
Technische Universität Darmstadt
Dissertation, Erstveröffentlichung
Kurzbeschreibung (Abstract)
Collinear laser spectroscopy is a versatile technique to study properties of nuclear ground states by the signature of nuclear structure encoded in the optical spectrum. Its sensitivity has been recently improved by the combination with bunched and cooled beams delivered from gas filled radio frequency quadrupole ion traps. In this work a new data acqusition system called TILDA (Triga Laser Data Acquisition) was developed at the TRIGA research reactor in Mainz and transferred to the COLLAPS experiment at ISOLDE/CERN where it was applied for the first time for laser spectroscopy of Ni isotopes. TILDA is based on an field programmable gate array and allows to resolve the time structure of the resonance signal while the bunch traverses the optical detection region with a time resolution of 10 ns. This allows for a detailed analysis of the bunch structure during the measurement but also in the off-line analysis. With the new data acquisition system, the proton magic nickel (Z=28) chain was investigated and the isotopes 58-68,70-Ni were measured at the COLLAPS experiment in the [Ar]3d9[2D5/2]4s 3D3 -> [Ar]3d9[2D5/2]4p 3P2 transition of neutral nickel. The change in the mean-square charge radius drc2 was extracted relative to the reference isotope 60-Ni. An increase in the differential change in drc2 across the neutron sub-shell gap at N=40 is observed. Results are compared with nuclear density functional theory calculations and show surprisingly less agreement than in other elements across shell closures in Ca, Cd, Sn or Pb. The isotope 68-Ni is of special interest. It is now the first short-lived isotope in which the root-mean-square charge radius rc and the dipole polarizability are known and this provides a benchmark to investigate the predictive power of several interactions based on chiral effective field theory embodied in coupled-cluster calculations. This is shown in this work in comparison to a similar test case in the doubly magic 48-Ca. In both cases, theory matched the experimental findings when 3-particle-3-hole excitations in the ground state were included in the coupled-cluster calculations. The determined hyperfine structure constants agree with the literature and are up to two orders of magnitude more precise than the previous values. The extracted moments indicate a strongly mixed wave-function especially at the I=3/2 states but a single-particle like behavior in the I=1/2 isotopes especially for 67-Ni right at the sub-shell closure.
Typ des Eintrags: | Dissertation | ||||
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Erschienen: | 2019 | ||||
Autor(en): | Kaufmann, Simon | ||||
Art des Eintrags: | Erstveröffentlichung | ||||
Titel: | Laser spectroscopy of nickel isotopes with a new data acquisition system at ISOLDE | ||||
Sprache: | Englisch | ||||
Referenten: | Nörtershäuser, Prof. Dr. Wilfried ; Aumann, Prof. Dr. Thomas | ||||
Publikationsjahr: | 2019 | ||||
Ort: | Darmstadt | ||||
Datum der mündlichen Prüfung: | 4 November 2019 | ||||
URL / URN: | https://tuprints.ulb.tu-darmstadt.de/9286 | ||||
Kurzbeschreibung (Abstract): | Collinear laser spectroscopy is a versatile technique to study properties of nuclear ground states by the signature of nuclear structure encoded in the optical spectrum. Its sensitivity has been recently improved by the combination with bunched and cooled beams delivered from gas filled radio frequency quadrupole ion traps. In this work a new data acqusition system called TILDA (Triga Laser Data Acquisition) was developed at the TRIGA research reactor in Mainz and transferred to the COLLAPS experiment at ISOLDE/CERN where it was applied for the first time for laser spectroscopy of Ni isotopes. TILDA is based on an field programmable gate array and allows to resolve the time structure of the resonance signal while the bunch traverses the optical detection region with a time resolution of 10 ns. This allows for a detailed analysis of the bunch structure during the measurement but also in the off-line analysis. With the new data acquisition system, the proton magic nickel (Z=28) chain was investigated and the isotopes 58-68,70-Ni were measured at the COLLAPS experiment in the [Ar]3d9[2D5/2]4s 3D3 -> [Ar]3d9[2D5/2]4p 3P2 transition of neutral nickel. The change in the mean-square charge radius drc2 was extracted relative to the reference isotope 60-Ni. An increase in the differential change in drc2 across the neutron sub-shell gap at N=40 is observed. Results are compared with nuclear density functional theory calculations and show surprisingly less agreement than in other elements across shell closures in Ca, Cd, Sn or Pb. The isotope 68-Ni is of special interest. It is now the first short-lived isotope in which the root-mean-square charge radius rc and the dipole polarizability are known and this provides a benchmark to investigate the predictive power of several interactions based on chiral effective field theory embodied in coupled-cluster calculations. This is shown in this work in comparison to a similar test case in the doubly magic 48-Ca. In both cases, theory matched the experimental findings when 3-particle-3-hole excitations in the ground state were included in the coupled-cluster calculations. The determined hyperfine structure constants agree with the literature and are up to two orders of magnitude more precise than the previous values. The extracted moments indicate a strongly mixed wave-function especially at the I=3/2 states but a single-particle like behavior in the I=1/2 isotopes especially for 67-Ni right at the sub-shell closure. |
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URN: | urn:nbn:de:tuda-tuprints-92866 | ||||
Sachgruppe der Dewey Dezimalklassifikatin (DDC): | 500 Naturwissenschaften und Mathematik > 530 Physik | ||||
Fachbereich(e)/-gebiet(e): | 05 Fachbereich Physik 05 Fachbereich Physik > Institut für Kernphysik 05 Fachbereich Physik > Institut für Kernphysik > Experimentelle Kernphysik 05 Fachbereich Physik > Institut für Kernphysik > Experimentelle Kernphysik > Atom- und Kernphysik radioaktiver Nuklide |
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Hinterlegungsdatum: | 17 Nov 2019 20:55 | ||||
Letzte Änderung: | 17 Nov 2019 20:55 | ||||
PPN: | |||||
Referenten: | Nörtershäuser, Prof. Dr. Wilfried ; Aumann, Prof. Dr. Thomas | ||||
Datum der mündlichen Prüfung / Verteidigung / mdl. Prüfung: | 4 November 2019 | ||||
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