MINISTRY OF EDUCATION VIETNAM ACADEMY AND TRAINING OF SCIENCE AND TECHNOLOGY GRADUATE UNIVERSITY OF SCIENCE AND TECHNOLOGY ----------------------------- BÙI MINH HUỆ STUDY OF ISOMERIC RATIO AND RELATED EFFECTS IN PHOTONUCLEAR AND NEUTRON CAPTURE REACTIONS ATOMIC AND NUCLEAR PHYSICS DOCTORAL THESIS Ha Noi – 2022 BỘ GIÁO DỤC VÀ ĐÀO TẠO VIỆN HÀN LÂM KHOA HỌC VÀ CÔNG NGHỆ VIỆT NAM HỌC VIỆN KHOA HỌC VÀ CÔNG NGHỆ ----------------------------- BÙI MINH HUỆ NGHIÊN CỨU TỶ SỐ ĐỒNG PHÂN VÀ CÁC HIỆU ỨNG LIÊN QUAN TRONG PHẢN ỨNG QUANG HẠT NHÂN VÀ PHẢN ỨNG BẮT NEUTRON LUẬN ÁN TIẾN SỸ VẬT LÝ NGUYÊN TỬ VÀ HẠT NHÂN Hà Nội – 2022 MINISTRY OF EDUCATION VIETNAM ACADEMY AND TRAINING OF SCIENCE AND TECHNOLOGY GRADUATE UNIVERSITY OF SCIENCE AND TECHNOLOGY ----------------------------- BÙI MINH HUỆ Major: Atomic and Nuclear Physics Code: 9440106 STUDY OF ISOMERIC RATIO AND RELATED EFFECTS IN PHOTONUCLEAR AND NEUTRON CAPTURE REACTIONS ATOMIC AND NUCLEAR PHYSICS DOCTORAL THESIS SUPERVISORS: 1. Dr Trần Đức Thiệp 2. Sergey Mikhailovich Lukyanov Ha Noi – 2022 i Declaration of Authorship I, Bui Minh Hue, declare that this thesis titled, “STUDY OF ISOMERIC RATIO AND RELATED EFFECTS IN PHOTONUCLEAR AND NEUTRON CAPTURE REACTIONS” and the work pre- sented in it are my own. I confirm that: • This work was done wholly or mainly while in candidature for a research degree at the Graduate University of Science and Technology.
• Where any part of this thesis has previously been submitted for a degree or any other qualification at this Graduate University or any other institution, this has been clearly stated. • The data in this thesis have not been used in other publications by anyone else. • Where I have consulted the published work of others, this is always clearly attributed. • Where I have quoted from the work of others, the source is always given.
With the exception of such quotations, this thesis is entirely my own work. • I have acknowledged all main sources of help. Signed: Date: ii Abstract The isomeric ratios (IRs) of 152m1,m2 Eu, 195m,g;197m,g Hg, 115m,g Cd, 109m,g Pd, 137m,g Ce and 81m,g Se pro- duced from photonuclear reactions (γ, n) with bremsstrahlung endpoint energies in Giant Dipole Res- onance region and that of 115m,g;117m,g Cd, 109m,g;111m,g Pd, 137m,g Ce and 81m,g Se in thermal-epithermal neutron capture reactions (n, γ) have been determined experimentally by using the activation tech- nique and off-line γ-ray spectroscopy measurement. The bremsstrahlung photons and neutrons were generated using the MT-25 Microtron of the Flerov Laboratory of Nuclear Reaction (FLNR), JINR, Dubna, Russia.
The activity of radioisotopes was determined with a HPGe detector together with es- sential corrections. This work reports, obtained from (γ, n) reactions, the IRs of 195m,g Hg withing 14 - 24 MeV, 197m,g Hg within 18 - 24 Mev, and 152m1,m2 Eu at 19, 21 and 23 Mev for the first time. More- over, the obtained results of 109m,g;111m,g P d and 115m,g;117m,g Cd in mixed thermal-resonant neutron capture reactions (n, γ) as well as that of 111m,g P d in resonance neutron capture reaction (n, γ) have been the first measurements. The impact of four effects including the nucleon configuration, spin dif- ference, excitation energy, and reaction channel effect on the experimental IRs was investigated.
The measured IRs were compared not only with the literature but also with the theoretically calculated IRs for the cases in the photonuclear reaction. The calculated IRs were yielded from TALYS 1.95 code- based calculated cross section in conjunction with GEANT4 toolkit-based simulated bremsstrahlung. The six level density models and eight radiative strength functions were taken into consideration for the theoretical calculations. iii Acknowledgements Honestly, I could not complete this thesis without the support and help of many people.
First and foremost, I owe special and great thanks to my supervisors, Prof.Tran Duc Thiep and Dr.Sergey Mikhailovich Lukyanov, for allowing me to start my Ph. and for their guidance, support, and inspiration. I am always thankful and consider them not only as my supervisor but also as my father. Tran Duc Thiep inspired and encouraged me on the abrupt road to science since 2012, when I started as a junior researcher at the Center for Nuclear Physics, Institute of Physics.
He was always available to illuminate my questions. I have gained much knowledge and experience in research, work, and life from him. I would also like to thank Dr. Truong Thi An, Dr.
Phan Viet Cuong and Dr. Le Tuan Anh for cooperating on the research projects. I am grateful to the Director, Mrs. Nguyen Thi Dieu Hong and staffs of Institute of Physics as well as my colleagues at the Center for Nuclear Physics for always helping, encouraging, and giving me convenience.
I had precious time and beautiful memories in Dubna. I always remember the warm hugs and the advice of Prof. I am thankful for the opportunity to exchange ideas and discuss work with my colleagues at the FLNR, JINR, made me feel like part of their group. I express my deepest gratitude to the MT-25 Microtron crew for providing the irradiation beam as well as the Chemistry of transactinides department of the Flerov Laboratory of Nuclear Reaction, JINR for furnishing the experimental apparatus.
I am also grateful to Mrs. Trinh Thi Thu My and my Vietnamese friends in Dubna for making my stay there very pleasant. I always had you by my side when taking a lunch break or gathering for BBQs on the Volga riverside. I am also thankful to Dr.Nishimura for lending me the equipment when I was at RIKEN.
I am grateful to the Board of Directors, and employees of Graduate University of Science and Technology for helping and supporting me throughout the process of doing this thesis. I would like to acknowledge the scientific research support for excellent Ph. students at the Graduate Univer- sity of Science and Technology in 2021. And I offer my gratitude and special thanks to Vingroup JSC and Ph.
Scholarship Programme of Vingroup Innovation Foundation (VINIF), Institute of Big Data funded and supported my Ph. studies within two years under VINIF. Last but not least, at the bottom of my heart, I would like to express my deepest gratitude to my family and parent-in-law for supporting and loving me during this long journey. I am very thankful for my aunt, N.Mai, for helping and taking care of me in the stressful period of finalizing this thesis.
Specially, I would like to spend a great thank my honey husband, who helped me a lot with coding. He has always encouraged and given me a happy life. He is the principal motivation for me to accomplish the present thesis. iv Contents Declaration of Authorship i Abstract ii Acknowledgements iii Contents iv List of Abbreviations vii List of Physical Quantities viii List of Tables x List of Figures xii Introduction xvi 1 Overview 1 1.1 Formation and classification of isomers .2 Isomeric ratio and related effects .1 Definition of isomeric ratio .2 Nuclear effects on isomeric ratio .3 Theoretical IR calculation .1 Formation of photonuclear reaction and photon sources .2 Cross-section of photonuclear reaction .4 Neutron capture reaction .1 Neutron and neutron sources .2 Neutron capture reaction (n, γ) .3 Neutron capture cross-section .5 Level density and γ-ray strength function .1 Nuclear level density .2 Gamma-ray strength function.
38 v 2 Experimental and theoretical methods 39 2. 40 Thermal and epithermal neutron source .4 Experimental IR determination .5 Spectrum analysis-necessary correction. 51 Self-absorption effect. 51 Coincidence summing corrections .2 Theoretical IR calculation in (γ, n) reaction .1 Bremsstrahlung spectra simulation in GEANT4 .2 Cross-section calculation in TALYS.
54 3 Results and Discussion 57 3.1 Isomeric Ratios in (γ, n) reactions .2 195m,g Hg and 197m,g Hg .2 Isomeric Ratios in (n, γ) reactions .1 109m,g Pd and 111m,g Pd .2 115m,g Cd and 117m,g Cd .3 Influence of nuclear channel effect on IRs in (γ, n) and (n, γ) reactions .4 IRs of 137m,g Ce, 115m,g Cd, 109m,g Pd, and 81m,g Se in inverse reactions .5 Theoretically calculated IRs in (γ, n) reactions .1 Bremsstrahlung spectra simulation .2 Cross-section calculation .3 IRs in (γ, n) reactions. 101 Conclusions and Outlook 118 List of Publications used for the Thesis content 122 References 124 A Geant4 simulation codes A1 A. A15 B Input file of TALYS code A18 C CERN ROOT analysis code to calculate IRs using energy flux spectra from GEANT4 and the cross-section outputs from TALYS A20 vii List of Abbreviations ADC Analogue to Digital Converter BCS Bardeen-Cooper-Schrieffer BSFG Back-Shifted Fermi Gas CTM Constant Temperature Model EXFOR Experimental Nuclear Reaction Data Library ENSDF Evaluated Nuclear Structure Data File FLNR Flerov Laboratory of Nuclear Reaction GDR Giant Dipole Resonance GEANT GEometry ANd Tracking GEDR Giant Electric Dipole Resonance GMR Giant Monopole Resonance GLO Generalized Lorentzian Model GQR Giant Quadrupole Resonance GSM Generalized Superfluid Model HF Hauser-Feshbach HFB Hartree-Fock-Bogolyubov HPGe High Purity Germanium HVM Huizenga-Vandebosch Model IAEA International Atomic Energy Agency IC Internal Conversion IR Isomeric Ratio JINR Joint Institute for Nuclear Research LD Level Density PDR Pygmy Dipole Resonance RIB Radioactive Ion Beam RIPL Reference Input Parameter Library QD Quasi-Deuteron QRPA Quasiparticle Random Phase Approximation SLO Standard Lorentzian γSF γ-ray Strength Function viii List of Physical Quantities A mass number a level density parameter ã asymptotic level density parameter a(Sn ) LD parameter at the neutron separation energy D0 experimental and theoretical average resonance spacing J angular momentum L multipolarity πi , πf parities of the initial and final states t1/2 half-life λ decay constant N neutron number Z atomic number R nuclear radius ϵ0 electric constant (= 8.8542 x 10−12 F/m) h̄ reduced Planck’s constant (= 1.s) c velocity of light (= 3.108 m/s) Eγ gamma-ray energy σi cross-section Y yield ϕ flux ρ level density fXL gamma strength function TXL transmission coefficient σ spin cut-off parameter Γ decay width γ shell damping parameter ∆ pairing energy δW shell correction energy Nlow , Ntop levels for the matching problem T nuclear temperature ix σ(Sn ) spin cut-off parameter at the neutron separation energy σ0 (M1) strengths of magnetic dipole resonance peak σ0 (E1) strengths of electric dipole resonance peak E(M1) centroid energy of magnetic dipole resonance peak E(E1) centroid energy of electric dipole resonance peak Γ(M1) width of magnetic dipole resonance peak Γ(E1) width of electric dipole resonance peak x List of Tables 2.1 Main parameters of MT-25 microtron [118, 120].2 Characteristics of irradiated samples, electron current and energy, and irradiation time.1 γ-rays decay properties of reaction products of 152m1,m2 Eu used in the IR calculation [140].2 A summary of corrections for self-absorption and summing coincidence for given γ-ray energies.3 The IR of 152m1,m2 Eu in the (γ, n) reaction.4 A summary of error sources considered in the IR calculation of 152m1,m2 Eu.5 γ-rays decay properties of reaction products of 195m,g Hg and 197m,g Hg used in the IR calculation [140].6 A summary of corrections for self-absorption and summing coincidence for given γ-ray energies.7 A summary of IRs determined for 195m,g;197m,g Hg isomeric pairs pro- duced in (γ, n) reaction [129].8 A summary of IRs determined for 197m,g Hg and 195m,g Hg isomeric pairs produced in various nuclear reactions.9 γ-rays decay properties of reaction products of 109m,g Pd and 111m,g Pd used in the IR calculation [140].10 A summary of corrections for self-absorption and summing coincidence for given γ-ray energies of 109m,g Pd and 111m,g Pd.11 A summary of IR results for 109m,g;111m,g Pd in thermal, resonance and mixed thermal-resonant neutron-induced reactions and also in a (γ, n) reaction.12 A summary of error sources considered in the IR calculation of 109m,g Pd.13 The decay properties of selected γ-rays for IR calculations for the 115m,g Cd and 117m,g Cd isomeric pairs [140].14 A summary of self-absorption and summing coincidence correction fac- tors for the γ-rays of interest of 115m,g;117m,g Cd [131].15 A summary of IRs results for 115m,g Cd and 117m,g Cd isomeric pairs pro- duced in different type of nuclear reactions.