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  • INSTITUTE OF NATURAL AND APPLIED SCIENCES

    UNIVERSITY OF CUKUROVA

    PhD THESIS

    Banu ÖZEL

    STUDY OF THE 112,120Sn (γ, γ′) REACTION AND SYSTEMATICS OF THE PYGMY DIPOLE RESONANCE AT THE Z=50 SHELL CLOSURE

    DEPARTMENT OF PHYSICS

    ADANA, 2008

  • ÇUKUROVA ÜNİVERSİTESİ

    FEN BİLİMLERİ ENSTİTÜSÜ

    112,120Sn(γ, γ′) REAKSİYONU VE Z=50 KAPALI KABUKLARINDA PYGMY

    DİPOL REZONANSI SİSTEMATİĞİNİN İNCELENMESİ

    Banu ÖZEL

    DOKTORA TEZİ

    FİZİK ANABİLİM DALI

    Bu tez ......................... tarihinde aşağıdaki jüri üyeleri tarafından oybirliği/oyçokluğu ile kabul edilmiştir.

    İmza............................. Prof.Dr. Süleyman GÜNGÖR 1. DANIŞMAN

    İmza............................. Prof.Dr. Peter von NEUMANN-COSEL 2. DANIŞMAN

    İmza............................. Prof.Dr. Metin ÖZDEMİR ÜYE

    İmza............................. Prof.Dr. Sefa ERTÜRK ÜYE

    İmza............................. Prof.Dr. Gülsen ÖNENGÜT ÜYE

    Bu tez Enstitümüz Fizik Anabilim Dalında hazırlanmıştır. Kod No:

    Prof.Dr. Aziz ERTUNÇ Enstitü Müdürü İmza ve Mühür

    Bu Çalışma DFG-SFB634, Erasmus-Sokrates Student Exchange Program ve DAAD Tarafından Desteklenmiştir.

    Not: Bu tezde kullanılan özgün ve başka kaynaktan yapılan bildirişlerin, çizelge, şekil ve fotoğ- rafların kaynak gösterilmeden kullanımı, 5846 sayılı Fikir ve Sanat Eserleri Kanunundaki hüküm- lere tabidir.

  • ÖZ

    DOKTORA TEZİ

    112,120Sn(γ, γ′) REAKSİYONU VE Z=50 KAPALI KABUKLARINDA PYGMY

    DİPOL REZONANSI SİSTEMATİĞİNİN İNCELENMESİ

    Banu ÖZEL

    ÇUKUROVA ÜNİVERSİTESİ

    FEN BİLİMLERİ ENSTİTÜSÜ

    FİZİK ANABİLİM DALI

    Danışman: Prof.Dr. Süleyman GÜNGÖR 2. Danışman: Prof.Dr. Peter von NEUMANN-COSEL

    Yıl: 2008, Sayfa: 75

    Jüri: Prof.Dr. Süleyman GÜNGÖR

    Prof.Dr. Peter von NEUMANN-COSEL Prof.Dr. Metin ÖZDEMİR Prof.Dr. Sefa ERTÜRK Prof.Dr. Gülsen ÖNENGÜT

    Bu tezde S-DALINAC süper iletken elektron lineer hızlandırıcısında gerçekleştirilen 112,120Sn(γ, γ′) reaksiyonları Bremsstrahlung spektrumunun farklı son nokta enerjileri için nötron ayrışma enerjisinin altındaki bölgelerde çalışılmıştır. 112Sn çekirdeği için 9.5 MeV‘ye, 120Sn çekirdeği için 7.5 ve 9.1 MeV‘ye kadar dipol geçiş şiddetleri dağılımı oluşturulmuştur. Elde edilen sonuçlar hali hazırda varolan 116,124Sn (Govaert, ve ark., 1998) verileri ile birlikte nötron fazlalığı olan çekirdeklerde bulunan pygmy dipol rezo- nansı olarak adlandırılan yapı hakkında bilgi edinmemizi sağlamıştır. Buna ek olarak parçalanma analizi denilen bir analiz metodu foton saçılması ile elde edilmiş olan spek- trumlara, parçalanmadan kaynaklanan ve fonda bulunan çözülmemiş geçiş şiddetlerinin miktarlarını tahmin edebilmek amacıyla uygulanmıştır.

    Sonuçlar quasiparticle phonon modeli ve relativistik quasiparticle RPA ile karşılaştırılmıştır.

    Anahtar Kelimeler: Pygmy Dipol Rezonansı, E1 geçiş şiddeti, nükleer rezonans fluo- resans metodu, parçalanma analizi

    I

  • ABSTRACT

    PhD THESIS

    STUDY OF THE 112,120Sn (γ, γ′) REACTION AND SYSTEMATICS OF THE

    PYGMY DIPOLE RESONANCE AT THE Z=50 SHELL CLOSURE

    Banu ÖZEL

    DEPARTMENT OF PHYSICS

    INSTITUTE OF NATURAL AND APPLIED SCIENCES

    UNIVERSITY OF ÇUKUROVA

    Supervisor: Prof.Dr. Süleyman GÜNGÖR 2. Supervisor: Prof.Dr. Peter von NEUMANN-COSEL

    Year: 2008, Pages: 75

    Jury: Prof.Dr. Süleyman GÜNGÖR

    Prof.Dr. Peter von NEUMANN-COSEL Prof.Dr. Metin ÖZDEMİR Prof.Dr. Sefa ERTÜRK Prof.Dr. Gülsen ÖNENGÜT

    In this thesis the 112,120Sn(γ, γ′) reactions are studied at different endpoint energies of the incident bremsstrahlung spectrum below the neutron separation energies at the super- conducting Darmstadt electron linear accelerator S-DALINAC. Dipole transition strength distributions are extracted for 112Sn up to 9.5 MeV and for 120Sn up to 9.1 MeV. A concen- tration of dipole excitations is observed between 5 and 8 MeV. Furthermore a fluctuation analysis is applied to the photon scattering spectra to estimate the amount of the unre- solved strength hidden in background due to fragmentation of the strength. Together with existing data for 116,124Sn (Govaert, et al., 1998) this provides a set of information on the structure of the so-called pygmy dipole resonance (PDR) in the stable neutron-rich tin nuclei.

    The results are compared to microscopic quasiparticle-phonon model and relativistic quasiparticle RPA calculations.

    Key Words: Pygmy Dipole Resonance, E1 transition strength, Nuclear Resonance Fluo- rescence, fluctuation analysis

    II

  • ACKNOLEDGEMENTS

    This work would not have been imaginable without help and support of many people

    who also I have been not mentioned directly their name at this place.

    I would like to express my deep and sincere gratitude to Prof. Dr. Peter von Neumann-

    Cosel for the supervision of my work. His very broad knowledge, help and suggestions

    were highly important for me and absolutely crucial in bringing this thesis to completion.

    I would like to thank Prof. Dr. h. c. mult. Achim Richter who kindly accepted me in

    his group in Institut für Kernphysik (IKP) at Technische Universität Darmstadt.

    Further on I would like to thank my second supervisor Prof. Dr. Süleyman Güngör for

    his continuous support and care during my stay in Çukurova University and in Germany.

    I would like to acknowledge Prof. Dr. Sefa Ertürk who introduced me to the field of

    experimental nuclear physics and supported me during all stage of my scientific work.

    I am also indebted to Prof. Dr. Joachim Enders, Dr. Yaroslav Kalmykov for numerous

    discussion during my work.

    I owe my sincere gratitude to my colleges at IKP: Dr. Stephan Volz, Dr. Deniz

    Savran, Dr. Kai Lindenberg, Linda Schnorrenberger, Jens Hasper, Michael Elvers, Iryna

    Poltoratska who helped me during my experiments and performing the analysis.

    I am very grateful to Dr. Nadia Tsoneva, Dr. V.Yu. Ponomarev, Dr. Nils Paar for pro-

    viding theoretical calculations and their fruitful suggestions in theoretical interpretation

    of the experimental results.

    I address my heartfelt gratitude to Dr. Harald Genz and Sabine Genz for their help,

    care, support and valuable friendship. I will never forget you.

    I wish to thank head of our department, Prof Dr. Yüksel Ufuktepe and Prof. Dr. Metin

    Özdemir from Çukurova University for their understanding, help and support.

    I wish to express my warm thanks to Dilek Koyuncu Özen, Cem Özen, Numan

    Bakırcı, Ayşe Seyhan, Yiğit Yıldız, Sarla Rathi, Barbara Sulignano, Haris Djapo. I am

    very happy to meet with you.

    Finally I would like to thank to my parents and my brother Tayfun for support, under-

    standing and being always together with me. Particularly I would like to express my most

    important thanks to my fiance, Dr. Stanislav Tashenov for his love, encouragement and

    patience during my work.

    III

  • TABLE OF CONTENTS PAGE

    ÖZ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I

    ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II

    ACKNOLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III

    TABLE OF CONTENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV

    LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VI

    LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VII

    LIST OF SYMBOLS AND ABBREVIATIONS . . . . . . . . . . . . . . . . . . . IX

    1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

    2 PREVIOUS WORKS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

    3 MATERIAL and METHOD . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

    3.1 Collective Excitations in Nuclei . . . . . . . . . . . . . . . . . . . . . . 5

    3.1.1 Giant Resonances . . . . . . . . . . . . . . . . . . . . . . . . . . 5

    3.1.1.1 Classification of Giant Resonances . . . . . . . . . . . 5

    3.1.2 Electric Dipole Excitations in Nuclei . . . . . . . . . . . . . . . 8

    3.1.2.1 Giant Dipole Resonance . . . . . . . . . . . . . . . . . 9

    3.1.2.2 Pygmy Dipole Resonance . . . . . . . . . . . . . . . . 10

    3.2 Nuclear Resonance Fluorescence (NRF) Method . . . . . . . . . . . . . 13

    3.2.1 Integrated Cross Section . . . . . . . . . . . . . . . . . . . . . . 15

    3.2.2 Transition Width and Transition Strength . . . . . . . . . . . . . 17

    3.2.3 Angular Distribution . . . . . . . . . . . . . . . . . . . . . . . . 18

    3.3 Photon Scattering Experiments at the S-DALINAC . . . . . . . . . . . . 21

    3.3.1 The S-DALINAC . . . . . . . . . . . . . . . . . . . . . . . . . . 21

    3.3.2 NRF Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

    3.3.3 Detectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

    IV