Resumen de Nuclear structure studies in the vicinity of the doubly-magic 132Sn nucleus

Lucía Caceres Monllor

• Contents 1 Introduction 7 2 Motivation 11 2.1 The Nuclear Shell Model . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.1.1 Empirical Shell Model . . . . . . . . . . . . . . . . . . . . . . . 12 2.1.2 Realistic Shell Model . . . . . . . . . . . . . . . . . . . . . . . . 13 2.2 Electromagnetic transitions . . . . . . . . . . . . . . . . . . . . . . . . 13 2.2.1 The internal electron conversion . . . . . . . . . . . . . . . . . . 13 2.2.2 Electromagnetic transition operators . . . . . . . . . . . . . . . 14 2.3 Nuclear Isomerism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.4 Nuclear Structure near the doubly-magic 132Sn . . . . . . . . . . . . . . 17 2.4.1 Single particle energy levels in 132Sn . . . . . . . . . . . . . . . . 17 2.4.2 ¯-decay Spectroscopy Studies . . . . . . . . . . . . . . . . . . . 20 2.4.3 r-Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3 Experimental Techniques 29 3.1 Production of exotic nuclei . . . . . . . . . . . . . . . . . . . . . . . . . 31 3.1.1 Projectile fragmentation . . . . . . . . . . . . . . . . . . . . . . 31 3.1.2 In-ight ssion . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 3.2 The FRagment Separator (FRS) at GSI . . . . . . . . . . . . . . . . . 33 3.2.1 B¿-¢E-B¿ method . . . . . . . . . . . . . . . . . . . . . . . . . 35 3.2.2 The FRS particle identication detectors . . . . . . . . . . . . . 37 3.2.2.1 The Multi Wire Proportional Counter (MWPC) . . . . 37 3.2.2.2 The MUlti Sampling Ionization Chamber (MUSIC) detector . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 3.2.2.3 The Scintillators SCI1, SCI2 and SCI3 . . . . . . . . . 39 3.3 Monte-Carlo simulations . . . . . . . . . . . . . . . . . . . . . . . . . . 40 3.4 Calibration of the FRS . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 3.4.1 Calibration of the MWPC detector . . . . . . . . . . . . . . . . 42 3.4.2 Calibration of the MUSIC detector . . . . . . . . . . . . . . . . 43 3.4.3 Calibration of the the time-of-ight detectors . . . . . . . . . . 45 3.5 Particle Identication . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 3.6 The RISING °-array . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 3.6.1 The Cluster detectors . . . . . . . . . . . . . . . . . . . . . . . . 49 3.6.2 °-Ray add-back conditions . . . . . . . . . . . . . . . . . . . . 52 3.7 Alternative experimental techniques . . . . . . . . . . . . . . . . . . . . 53 3 4 CONTENTS 4 Particle identication analysis 55 4.1 Isotope identication . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 5 Analysis of the delayed °-ray spectra and Results 61 5.1 The nucleus 130Cd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 5.1.1 Eect of the particle selection on the °-ray spectrum . . . . . . 66 5.1.1.1 Contamination in the ° energy spectrum caused by reactions in the degrader at S4 . . . . . . . . . . . . . . 66 5.1.1.2 Ion tracking detectors: The eect of the conditions on the MPWC detectors . . . . . . . . . . . . . . . . . . . 67 5.1.1.3 Reactions in the MUSIC detectors . . . . . . . . . . . 67 5.2 The nucleus 128Cd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 5.3 The nucleus 126Cd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 5.4 The nucleus 131In . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 6 Discussion 99 6.1 N = 82 Shell Quenching . . . . . . . . . . . . . . . . . . . . . . . . . . 99 6.1.1 Astrophysical implications . . . . . . . . . . . . . . . . . . . . . 103 6.2 Empirical j2 two-body interaction . . . . . . . . . . . . . . . . . . . . . 103 6.3 Proton-Neutron interaction in neutron rich nuclei . . . . . . . . . . . . 104 7 Summary 109 Apendix A: Additional coincidence energy spectra gated by the ° transitions observed in the 126Cd isomeric decay 113 Apendix B: Time distributions of the ° lines observed in the 126Cd isomeric decay 124 Bibliography 128