Universität zu Köln

Ley, Mario ORCID: 0000-0003-1453-070X (2025). Investigation of Seniority Conservation in the N = 50 Isotones using Lifetime Measurements. PhD thesis, Universität zu Köln.

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Abstract

In this doctoral thesis, new experimental findings for lifetimes of excited states in the N = 50 isotones 91Nb, 92Mo, 93Tc, 94Ru, and 95Rh are presented. The new data are the result of three experimental campaigns conducted at the Institute for Nuclear Physics at the University of Cologne employing the well established γ-γ fast-timing method using a hybrid setup of cerium-doped lanthanum bromide scintillation and high-purity germanium detectors. The nuclei were produced in fusion-evaporation reactions using the Cologne 10 MV FN Tandem accelerator and the emitted γ rays were detected using the HORUS spectrometer of the institute. The newly acquired data are compared with known experimental values from the literature and with shell-model calculation results. The data are also discussed in the context of potential signatures of partial seniority conservation versus an abrupt breakdown of seniority. The lifetime 92Mo was measured with high precision to determine the B(E2;4+→2+) transition strength with sufficiently low uncertainty. In particular this lifetime measurement allows to use the B(E2) values from the entire yrast 8+→6+→4+→2+→0+gs cascade to extract state-dependent effective charges with high accuracy. These effective charges are then applied within a single-j approximation to predict B(E2) transition strengths for the (9/2)3, (9/2)4 , and (9/2)5 systems in the π1g9/2 shell, corresponding to the nuclei 93Tc, 94Ru, and 95Rh, respectively. Furthermore, this ansatz enabled the extraction of admixture coefficients for the mixing of states with the same angular momentum but different seniority, by minimizing the deviation between the theoretical predictions based on the single-j approach and the experimental data.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Ley, Mario mley@ikp.uni-koeln.de https://orcid.org/0000-0003-1453-070X UNSPECIFIED
URN:	urn:nbn:de:hbz:38-793935
Date:	2025
Place of Publication:	Köln
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Physics > Institute for Nuclear Physics
Subjects:	Physics
Uncontrolled Keywords:	Keywords Language Seniority UNSPECIFIED Lifetime Measurements UNSPECIFIED N = 50 Isotones UNSPECIFIED
Date of oral exam:	14 October 2025
Referee:	Name Academic Title Jolie, Jan Prof. Dr. Dr. h.c.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/79393