Fernández Martínez, Guillermo (2018)
Measurement of the lifetimes of excited states in neutron-rich Ce isotopes.
Technische Universität Darmstadt
Dissertation, Erstveröffentlichung
Kurzbeschreibung (Abstract)
Neutron-rich cerium isotopes are located in the region of the nuclear chart some neutrons and protons above the doubly-magic ${}^{132}$Sn, where a variety of shape phenomena are expected. Among them, the evolution of the quadrupole collectivity going away from the shell closures, or the octupole deformation in the vicinity of $Z=56$ and $N=88$ stand out.
The goal of the present work is, hence, the study of the structural evolution of neutron-rich cerium isotopes, through the knowledge of the reduced transition strengths between their low-lying excited states. These values have been derived from the direct measurement of the lifetimes of excited states.
The fast-timing experimental campaign was carried out at the Argonne National Laboratory, where a large variety of nuclei was produced in the spontaneous fission of ${}^{252}$Cf. In order to ensure the selection of the cerium isotopes of interest, one hemisphere of the Gammasphere array, consisting of 51 high-resolution HPGe detectors, was used. Additionally, 25 ultra-fast LaBr$_3$(Ce) detectors from the NuSTAR-FATIMA collaboration allowed to measure the lifetimes of the excited states of these selected isotopes by means of the Generalised Centroid Difference Method. The use of such a large combined array of HPGe and LaBr$_3$(Ce) detectors is unprecedented in a fast-timing experiment.
Several lifetimes of low-lying excited states in the even-even ${}^{146-150}$Ce isotopes have been obtained, four of them for the first time. The observed trend of the reduced transition strengths along the isotopic chain, together with the systematics of the excitation energies confirm the increasing collectivity towards more prolate shapes. These experimental results have been compared to new theoretical calculations obtained within the Symmetry Conserving Configuration Mixing and Shell Model approaches. Both theoretical predictions seem to properly reproduce the experimental results.
| Typ des Eintrags: | Dissertation | ||||
|---|---|---|---|---|---|
| Erschienen: | 2018 | ||||
| Autor(en): | Fernández Martínez, Guillermo | ||||
| Art des Eintrags: | Erstveröffentlichung | ||||
| Titel: | Measurement of the lifetimes of excited states in neutron-rich Ce isotopes | ||||
| Sprache: | Englisch | ||||
| Referenten: | Kröll, Prof. Dr. Thorsten ; Enders, Prof. Dr. Joachim | ||||
| Publikationsjahr: | 10 April 2018 | ||||
| Ort: | Darmstadt | ||||
| Datum der mündlichen Prüfung: | 7 Mai 2018 | ||||
| URL / URN: | https://tuprints.ulb.tu-darmstadt.de/7818 | ||||
| Kurzbeschreibung (Abstract): | Neutron-rich cerium isotopes are located in the region of the nuclear chart some neutrons and protons above the doubly-magic ${}^{132}$Sn, where a variety of shape phenomena are expected. Among them, the evolution of the quadrupole collectivity going away from the shell closures, or the octupole deformation in the vicinity of $Z=56$ and $N=88$ stand out. The goal of the present work is, hence, the study of the structural evolution of neutron-rich cerium isotopes, through the knowledge of the reduced transition strengths between their low-lying excited states. These values have been derived from the direct measurement of the lifetimes of excited states. The fast-timing experimental campaign was carried out at the Argonne National Laboratory, where a large variety of nuclei was produced in the spontaneous fission of ${}^{252}$Cf. In order to ensure the selection of the cerium isotopes of interest, one hemisphere of the Gammasphere array, consisting of 51 high-resolution HPGe detectors, was used. Additionally, 25 ultra-fast LaBr$_3$(Ce) detectors from the NuSTAR-FATIMA collaboration allowed to measure the lifetimes of the excited states of these selected isotopes by means of the Generalised Centroid Difference Method. The use of such a large combined array of HPGe and LaBr$_3$(Ce) detectors is unprecedented in a fast-timing experiment. Several lifetimes of low-lying excited states in the even-even ${}^{146-150}$Ce isotopes have been obtained, four of them for the first time. The observed trend of the reduced transition strengths along the isotopic chain, together with the systematics of the excitation energies confirm the increasing collectivity towards more prolate shapes. These experimental results have been compared to new theoretical calculations obtained within the Symmetry Conserving Configuration Mixing and Shell Model approaches. Both theoretical predictions seem to properly reproduce the experimental results. |
||||
| Alternatives oder übersetztes Abstract: |
|
||||
| URN: | urn:nbn:de:tuda-tuprints-78184 | ||||
| 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 |
||||
| Hinterlegungsdatum: | 21 Okt 2018 19:55 | ||||
| Letzte Änderung: | 21 Okt 2018 19:55 | ||||
| PPN: | |||||
| Referenten: | Kröll, Prof. Dr. Thorsten ; Enders, Prof. Dr. Joachim | ||||
| Datum der mündlichen Prüfung / Verteidigung / mdl. Prüfung: | 7 Mai 2018 | ||||
| Export: | |||||
| Suche nach Titel in: | TUfind oder in Google | ||||
 |
Frage zum Eintrag |
Optionen (nur für Redakteure)
 |
Redaktionelle Details anzeigen |
Drucken
Impressum