| Title: |
Study of the radiative deexcitation of ¹⁷⁷Lu ; Étude de la désexcitation radiative du ¹⁷⁷Lu |
| Authors: |
Pottier, Mathilde |
| Contributors: |
Laboratoire Matière sous Conditions Extrêmes (LMCE); DAM Île-de-France (DAM/DIF); Direction des Applications Militaires (DAM); Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction des Applications Militaires (DAM); Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay; Université Paris-Saclay; Olivier Roig |
| Source: |
https://theses.hal.science/tel-05313719 ; Nuclear Experiment [nucl-ex]. Université Paris-Saclay, 2025. English. ⟨NNT : 2025UPASP071⟩. |
| Publisher Information: |
CCSD |
| Publication Year: |
2025 |
| Subject Terms: |
Gamma-ray strength function; Nuclear reaction; Oslo method; Nuclear level density; Fonction de force gamma; Réaction nucléaire; Méthode d'Oslo; Densité de niveaux nucléaire; [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]; [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det] |
| Description: |
The nuclear level density and the gamma-ray strength function are two essential ingredients for understanding how nuclei deexcite by γ-ray emission. The former describes the number of excited levels accessible by the nucleus per unit of energy, and the latter characterizes the probability of deexcitation from one level to another by γ-ray emission. This thesis sets out to determine these two functions experimentally for ¹⁷⁷Lu. The reaction studied is ¹⁷⁶Lu(d,p)¹⁷⁷Lu, which, thanks to the new SFγNCS detector, enables the excitation energy of ¹⁷⁷Lu and the γ-ray cascade emitted by the nucleus formed to be measured simultaneously. The data acquired are analyzed using the Oslo method, which allows simultaneous determination of the two functions of interest. For the first time, these functions are determined experimentally for ¹⁷⁷Lu. The same analysis is carried out on the γ-ray cascades feeding different isomers of ¹⁷⁷Lu, which are long-lived metastable states. The results are very similar to those obtained for all cascades, suggesting that the γ-ray strength function is independent of the energy, spin and parity of the initial and final levels, as predicted by the Brink-Axel hypothesis. The functions obtained are used as input parameters in reaction codes to determine the radiative neutron absorption cross section of ¹⁷⁶Lu. The calculations give values close to the experimental data without arbitrary normalization. The same functions can also be used to reproduce γ-ray spectra using deexcitation codes, provided that the initial spin distribution is known. Finally, the experiment gives access to the isomeric ratios and reveals that these states are populated by at least half of the γ-ray cascades. ; La densité de niveaux nucléaire et la fonction de force γ sont deux ingrédients essentiels pour comprendre la façon dont les noyaux se désexcitent par émission de rayons γ. La première décrit le nombre de niveaux excités accessibles par le noyau par unité d'énergie et la seconde caractérise la probabilité de ... |
| Document Type: |
doctoral or postdoctoral thesis |
| Language: |
English |
| Relation: |
NNT: 2025UPASP071 |
| Availability: |
https://theses.hal.science/tel-05313719; https://theses.hal.science/tel-05313719v1/document; https://theses.hal.science/tel-05313719v1/file/148716_POTTIER_2025_archivage.pdf |
| Rights: |
info:eu-repo/semantics/OpenAccess |
| Accession Number: |
edsbas.E8BD66D4 |
| Database: |
BASE |