Chirality in the ¹3Nd and ¹3Nd nuclei Bingfeng Lv To cite this version: Bingfeng Lv. Chirality in the ¹3Nd and ¹3Nd nuclei. Nuclear Experiment [nucl-ex]. Université Paris Saclay (COmUE), 2019. English. NNT : 2019SACLS353. tel-02347000 HAL Id: tel-02347000 https://tel.archives-ouvertes.fr/tel-02347000 Submitted on 5 Nov 2019 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Chirality in the 136Nd and 135Nd nuclei These` de doctorat de l’Universite´ Paris-Saclay prepar´ ee´ a` l’Universite´ Paris-Sud Ecole´ doctorale n◦576 particules hadrons energie´ et noyau: instrumentation, image, cosmos et simulation (PHENIICS) Specialit´ e´ de doctorat : Structure et reactions´ nucleaires´ These` present´ ee´ et soutenue a` Orsay, le 11 octobre 2019, par NNT : 2019SACLS353 BINGFENG LV Composition du Jury : MME AMEL KORICHI Directrice de Recherche, CSNSM Presidente´ MME ELENA LAWRIE Professeure associee,´ iThemba Labs, South Africa Rapporteur MME NADINE REDON Directrice de Recherche, IP2I Lyon Rapporteur M. ZHONG LIU Professeur des Universites,´ Chinese Academy of Sciences, IMP, China Examinateur M. COSTEL PETRACHE Professeur des Universites,´ Paris-Sud/Paris Saclay Directeur de these` 2 Acknowledgements I would like to express my sincere gratitude to those who helped me and shared their ex- periences during my PhD. The work presented here would have been impossible to conclude without their guidance and assistance. First and foremost, I would like to express my sincere gratitude to my supervisor Pro- fessor Costel Petrache, for his systematic teaching and training me in experimental nuclear structure research. It is my great honor to have a supervisor who is so famous and highly respected in the nuclear physics. Also, I want to express my deepest grateful to him for his take care of me, and all the things he has done for me even if he never told me. In addition, for sure, his personal qualities, like work hard, great passion for research, explorative spirit ......, will influence me more in the future. For me, he is not only a mentor in my work, but also in my life. I would like to also thank my CSNSM colleagues. Alain Astier help will never be for- gotten due to his selfless shared many data analysis skills used in present work. I feel very lucky that I had a very nice officemate, Etienne Dupont, who assisted me a lot in my daily life in France. I want to say "Merci beaucoup, monsieur Etienne Dupont ". I also would like to thank Amel Korichi, Araceli Lopez-Martens, Jérémie Jacob, Nicolas Dosme and all the other colleagues in CSNSM for their assistance. I also thank the nuclear structure group of IMP, Lanzhou, in particular, Xiaohong Zhou, my supervisor, also Guo Song and Jianguo Wang for initiating me in experimental nuclear physics research. In particular, I would like to thank Dr. Guo Song for establishing the colla- boration between Professor Costel Petrache group and the nuclear structure group in IMP, which provided me the opportunity to do my PhD in CSNSM, Orsay, France. Ialsowouldliketothankanotheroneofmysupervisors,WenhuiLongfromLanzhou University for his continue support and very wisdom advice for my future career. I would like to thank all our collaborators, in particular to Prof. Meng Jie and Dr. Qibo Chen for their excellent theoretical work made for the interpretation of the present data. I am thankful to the jury members of my PhD defense, Dr. Amel Korichi (CSNSM, Or- say), Dr. Elena Lawrie (iThemba Labs, South Africa), Dr. Nadine Redon (IP2I Lyon), and Dr. Zhong Liu (IMP, Lanzhou) for having spent their valuable time to evaluate my PhD work and read my thesis, also to give suggestions and comments on my manuscript. I would like to also thank the financial support of China Scholarship Council (CSC) and CSNSM, CNRS. Finally, I would like to express my heartfelt gratitude to my parents for their love, care and constant spiritual support in my 22 years student career. Also, thanks to my girl friend Cui Xiaoyun for her understanding, accompany and endless encouragement. 3 Contents Acknowledgements 3 1Introduction 17 1.1 Chirality.............................. 18 1.1.1 NuclearChirality . 19 1.1.2 Multiple chiral doublets (MχD) . 20 1.2 Fingerprints of the chiral bands . 21 1.2.1 Energyspectra ...................... 21 1.2.2 Electromagnetic transitions rates . 21 1.2.3 Other fingerprints . 22 1.3 Motivationofthisstudy . 23 1.4 Outline of thesis . 23 2Theoreticalbackgroud 25 2.1 Liquid drop model . 25 2.2 Theshellmodel.......................... 26 2.3 Thedeformedshellmodel . 28 2.3.1 Deformed parameters . 28 2.3.2 TheNilssonmodel . 32 2.4 Particle-rotor model . 37 2.4.1 Strong coupling . 38 2.4.2 Thedecouplinglimit . 38 2.4.3 Four-j shells particle-rotor model . 39 2.5 Cranked Nilsson-Strutinsky model . 41 2.5.1 Crankingmodel...................... 41 2.5.2 The rotating liquid drop model . 45 2.5.3 The configuration-dependent CNS approach . 46 2.6 Tilted axis cranking covariant density functional theory . 47 2.6.1 Tiltedaxiscranking . 47 2.6.2 TAC-CDFT ........................ 50 2.7 Transition probabilities . 52 5 6 CONTENTS 3Experimentaltechniques 53 3.1 Heavy-ion fusion-evaporation reactions . 53 3.2 Interaction mechanisms of the γ-rays with matter . 55 3.2.1 Photoelectricabsorption . 55 3.2.2 Comptonscattering. 55 3.2.3 Pair production . 56 3.3 High-purity Germanium γ-ray detector . 56 3.4 TheJUROGAMIIarray. 58 3.5 TheRITUgas-filledrecoilseparator. 59 3.6 TheGREATspectrometer . 61 3.7 Total-DataReadout(TDR) . 62 4Experimentaldetailsandprocessingofthedata 65 4.1 Experimentaldetails . 65 4.2 Data processing . 65 4.2.1 Energy calibrations and gain matching . 65 4.2.2 Efficiency calibrations for Ge detectors . 66 4.2.3 Doppler shift correction . 67 4.2.4 Add-back for the clover detectors . 67 4.2.5 Spin and parity assignments . 68 5Towardscompletespectroscopyof136Nd 71 5.1 Experimental results and level scheme . 71 5.1.1 The low-spin γ band and bands N1, N2 . 72 5.1.2 The medium-spin bands L and T . 73 5.1.3 Thedipolebands ..................... 75 5.1.4 The highly-deformed bands . 81 5.2 Discussion . 98 5.2.1 MχD interpretation of the chiral bands within TAC- CDFTframework..................... 98 5.2.2 MχD interpretation of the chiral bands within PRM framework . 103 5.2.3 CNS interpretation of all rotational bands . 108 6EvidenceofMχDintheodd-Anucleus135Nd 123 6.1 Introdution ............................ 123 6.2 Experimental results and level scheme . 124 6.3 Discussion . 127 7Searchforlong-livedisomericstates 139 7.1 Introduction . 139 7.2 The recoil-decay tagging technique . 139 7.3 Results of the focal plane . 140 CONTENTS 7 Synthèse 145 Conclusions and Outlook 147 Appendix A JUROGAM II detector angles 149 8 CONTENTS List of Figures 1.1 Left- and right-handed chiral systems for a triaxial odd-odd nucleus. The symbols J~, R~, ~j⌫,and~j⇡ denote respectively the total angular momentum, the angular momenta of the core, of the neutron and of the proton, respectively. Figure adopted from Ref. [1]. ........................... 19 1.2 The nuclides with chiral doublet bands (red circles) and MχD (blue pentagons) observed in the nuclear chart. The black squares represent stable nuclides. Figure adopted from Ref. [2]. 22 2.1 Schematic nuclear levels calculated by the shell model including the l2 and ~l ~s terms. Figure adapted from Ref. [3]. 29 · 2.2 The lowest four vibrations of a nucleus. The dashed lines show the spherical equilibrium shape and the solid lines show an in- stantaneous view of the vibrating surface. Figure adapted from Ref. [4]. .............................. 30 2.3 Plot of the Eq. 2.12,fork=1, 2, 3, corresponding to the increase in the axis lengths in the x, y,andz directions. Figure adopted from Ref. [5]. ........................... 31 2.4 Schematic of nuclear shapes with respect to the deformation parameters (β2, γ), as defined in the Lund convention. Figure adapted from Ref. [6]. ...................... 32 2.5 Schematic of the quantum numbers which can describe the de- formed nucleus. ⇤, ⌦, ⌃,andKaretheprojectionsoftheor- bital angular momentum l,ofthetotalangularmomentumof the particle j,ofthespinoftheparticles,andofthetotal angular momentum J onto the symmetry axis, respectively. In addition, R~ is the angular momentum of the core and M is the projection of the total angular momentum onto the laboratory axis. ................................ 34 2.6 Nilsson diagram for protons in the 50 Z 80 region showing the single-particle energies as a function of the deformation pa- rameter ✏2.For✏2 >0, corresponding to the prolate shape; for ✏2 =0, corresponding to the spherical shape; for ✏2 <0,corre- ⇡ sponding to the prolate shape. Labels obey the ⌦ [Nnz⇤] rule. 35 9 10 LIST OF FIGURES 2.7 Nilsson diagram for neutrons in the 50 N 80 region show- ing the single-particle energies as a function of the deformation parameter ✏2.For✏2 >0, corresponding to the prolate shape; for ✏2 =0, corresponding to the spherical shape; for ✏2 <0,corre- ⇡ sponding to the prolate shape. Labels obey the ⌦ [Nnz⇤] rule. 36 2.8 Schematic diagram of the strong coupling limit in the particle- rotor model. 39 2.9 Schematic diagram of the decoupling limit in the particle-rotor model. 39 2.10 Discrete symmetries of the mean field of a rotating triaxial re- flection symmetric nucleus. The axis of rotation (z)ismarked by the circular arrow. The rotational band structures associated with each symmetry type are presented on the right side.