Nuclear structure around doubly-magic nuclei

Abstract

U ovoj tezi smo ispitivali strukturu jezgara u okolini 68Ni kao i proizvodnju, razdvajanje i identifikaciju izotopa bogatih protonima koji se nalaze u okolini dvostruko magičnog jezgra 100Sn. U prvom delu smo diskutovali evoluciju kolektivnosti i sadejstvo između kolektivnih i pojedinačno-čestičnih stepeni slobode u jezgrima oko 68Ni. U GANIL-u smo merili vremena života u izotopima Zn u okolini N = 40 proizvedenih u duboko neelastičnim sudarima 238U + 70Zn. Koristili smo uređaj "plunger" i metod " recoil-distance Dopplershift". Jezgra od interesa su identifikovana korišćenjem VAMOS spektrometra, a gama zraci su identifikovani EXOGAM detektorom. Iz merenog vremena života je izvedena redukovana verovatnoća elektromagnetskih prelaza. Nekoliko tranzicija i vremena života su merene i objavljene po prvi put. Proračuni modela ljuske su korišćeni za analizu i diskusiju eksperimentalnih rezultata. U drugom delu, analizirano je i diskutovano delimično održanje "seniority" kvantnog broja u g9/2 ljusci i njegov uticaj na transfer jedne čestice u istoj ljusci. Treći deo obuhvata analizu test experimenta sprovedenog u institutu RIKEN (Japan). Cilj je bio da se ispitaju i procene dve konfiguracije BigRIPS separatora kako bi se optimizovala proizvodnja i selekcija 100Sn. Ova studija je potom korišćena da se podese parametri našeg narednog eksperimenta, koji je bio posvećen merenju intenziteta Gamow-Teller prelaza u raspadu 100Sn. Jezgra u okolini 100Sn su proizvedena fragmentacijom snopa 124Xe energije 345 MeV/u na berilijumskoj meti. Efikasni preseci proizvodnje jezgara u okolini 100Sn su mereni. Takođe, potraga za novim izotopima i izomerima u svim identifikovanim jezgrima je prikazana.

In this thesis we investigated the structure of nuclei around 68Ni as well as the production, separation and identification of proton-rich isotopes lying in the vicinity of the doubly-magic 100Sn nucleus. In the first part, we discuss the evolution of collectivity and the interplay between collective and single-particle degrees of freedom in nuclei around 68Ni. We measured lifetimes in Zn isotopes around N = 40 produced in 238U + 70Zn deep-inelastic collisions at GANIL. We used a plunger device and the recoil-distance Doppler-shift method. The nuclei of interest were identified by the VAMOS spectrometer and the -rays with the EXOGAM array. The reduced electromagnetic transitions probabilities were extracted from the lifetimes. Several transitions and lifetimes are reported for the first time. The experimental results are discussed in the framework of shell model calculations. In the second part, the partial conservation of seniority in the g9/2 shell and its influence on one-particle transfer is discussed. The third part presents the analysis of a test performed at RIKEN (Japan) to evaluate two settings of the BigRIPS separator for optimizing the production and selection of 100Sn. This study has been used to setup our subsequent experiment, dedicated to the measurement of the Gamow-Teller strength in the decay of 100Sn. Nuclei around 100Sn were produced by fragmentation of a 345 MeV/u 124Xe beam on a Be target. The production cross-sections of nuclei around 100Sn were measured. The search for new isotopes and new isomers in all identified nuclei is presented.