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 – 2023 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 – 2023 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 – 2023 ii Abstract The isomeric ratio (IR) of 152m1,m2 Eu, 195m,g;197m,g Hg, 115m,g Cd, 109m,g Pd, 137m,g Ce and 81m,g Se produced from photonuclear reactions (γ, n) with bremsstrahlung endpoint energies in the Giant Dipole Resonance region and IR 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 experimentally determined using the activation technique and measurement of off-line γ-ray spectroscopy. The bremsstrahlung photons and neutrons were generated using the MT-25 Microtron of the Flerov Laboratory of Nuclear Reaction (FLNR), JINR, Dubna, Russia.
Radioisotope activity was determined with a high-resolution γ-ray HPGe detector and dedicated analysis software. This work reports, obtained from reactions (γ, n), the IRs of 195m,g Hg within 14 - 24 MeV, 197m,g Hg within 18 - 24 MeV, and 152m1,m2 Eu at 19, 21 and 23 MeV for the őrst time. Furthermore, the IR results of 109m,g;111m,g Pd and 115m,g;117m,g Cd in mixed thermal resonant neutron capture reactions (n, γ), as well as those of 111m,g Pd in the resonance neutron capture reaction (n, γ) have been the őrst measurements. The impact of the nucleon conőguration, spin difference, excitation energy, and reaction channel effects on the experimental IRs was considered.
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 calculated cross sections based on TALYS 1.95 code in conjunction with simulated bremsstrahlung based on the GEANT4 toolkit. 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 for them and consider them not only my supervisor, but also 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 a lot of knowledge and experience from him in research, work, and life. 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 Board of Directors, Mrs.Nguyen Thi Dieu Hong, and the staff of the 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 the 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 very pleasant.
I always had you by my side when I took a lunch break or gathered 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 the Graduate University of Science and Technology (GUST) for helping and supporting me throughout the process of doing this thesis. I would like to acknowledge the scientiőc research support of the GUST for excellent Ph.
And I offer my gratitude and special thanks to Vingroup JSC and Ph. Scholarship Programme of Vingroup Innovation Foundation (VINIF), Institute of Big Data, for funding and supporting my Ph. studies within two years under the VINIF. Last but not least, from the bottom of my heart, I would like to express my deepest thanks to my family and my parents-in-law who supported and cherished me on this long journey.
I am very grateful to my aunt, N.Mai, for helping and taking care of me in the stressful period of őnalizing this thesis. Especially, I would like to thank my honey husband, Dr.Vi Ho Phong, for helping me a lot with coding. He has always encouraged and given me a happy life. He is the main motivation for me to carry out the present thesis.
iv Contents Declaration of Authorship i Abstract ii Acknowledgements iii Contents iv List of Abbreviations vii List of Physical Quantities ix List of Tables xi List of Figures xiii Introduction xvii 1 Overview 1 1.1 Formation and classiőcation of isomers .2 Isomeric ratio and related effects .1 Deőnition 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. 18 Above particle emission threshold up to 30 MeV. 19 Below particle emission threshold. 21 In the energy range of 30 to 140 MeV .4 Neutron capture reaction .1 Neutron and neutron sources .3 Neutron capture cross-section .5 Level density and γ-ray strength function .1 Nuclear level density .2 Gamma-ray strength function.
36 2 Experimental and theoretical methods 37 2. 39 Thermal and epithermal neutron source .4 Experimental IR determination .5 Spectrum analysis-necessary correction. 49 Self-absorption effect. 49 Coincidence summing corrections .2 Theoretical IR calculation in (γ, n) reaction .1 Bremsstrahlung spectra simulation in GEANT4 .2 Cross-section calculation in TALYS.
52 3 Results and Discussion 56 3.1 Isomeric Ratios in (γ, n) reactions .2 Hg and Hg .2 Isomeric Ratios in (n, γ) reactions .1 Pd and 111m,g Pd .2 Cd and 117m,g Cd .3 Inŕuence of nuclear channel effect on IRs in (γ, n) and (n, γ) reactions .4 IRs of Ce, Cd, Pd, and 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. 99 Conclusions and Outlooks 117 List of Publications used for the Thesis content 120 References 122 vi A Geant4 simulation codes A1 A. A15 B Input őle of TALYS code A18 C CERN ROOT analysis code to calculate IRs using energy ŕux 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 Superŕuid 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 ix 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 π i , πf parities of the initial and őnal 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 Eu energy of isomeric state Ed energy of ground state σi cross-section Y yield ϕ ŕux 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 x 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 xi List of Tables 2.1 Main parameters of MT-25 microtron [116, 118].2 Characteristics of the irradiated samples, electron current and energy, and irradiation time.1 γ-rays decay properties of the reaction products of 152m1,m2 Eu used in the IR calculation [138].2 A summary of corrections for self-absorption and summing coincidence for given γ-ray energies.3 The IR of 152m1,m2 Eu in reaction (γ, n).4 A summary of error sources considered in the IR calculation of 152m1,m2 Eu.5 γ-rays decay properties of the reaction products of 195m,g Hg and 197m,g Hg used in the IR calculation [138].6 A summary of corrections for self-absorption and summing coincidence for given γ-ray energies.7 Summary of IRs determined for 195m,g;197m,g Hg isomeric pairs produced in reaction (γ, n) [128].8 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 [138].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 the error sources considered in the IR calculation of 109m,g Pd.13 The decay properties of selected γ-rays for IR calculations for 115m,g Cd and 117m,g Cd isomeric pairs [138].14 A summary of self-absorption and summing coincidence correction fac- tors for the γ-rays of interest of 115m,g;117m,g Cd [130].15 A summary of IR results for 115m,g Cd and 117m,g Cd isomeric pairs pro- duced in different types of nuclear reactions.16 A summary of the error sources considered in the IR calculations of 115m,g;117m,g Cd.17 The IRs of 109m,g Pd in thermal, resonance and mixed thermal-resonant neutron capture reactions and in (γ, n) reaction.18 The IRs of 115m,g Cd produced in different nuclear reactions.19 Selected gamma rays and spectroscopic characteristic data [138].20 The IRs of the studied inverse reactions. 94 xiii List of Figures 1.1 Nuclear chart displaying isomeric states with T1/2 ≥ 100 ns (NUBASE 2020) [13].2 Organization of input-output ŕows and components of the nuclear model in the TALYS program.
Image taken from [56].3 The general total photon absorption cross-section below 30 MeV (taken from the presented slice of N.Tsoneva at ERICE2014).