Search for the scissors resonance in 182Ta

Brits, Christiaan Petrus (2016-12)

Thesis (MSc)--Stellenbosch University, 2016

Thesis

ENGLISH ABSTRACT :Relatively small changes to the overall shape of the photon strength function such as the scissors or pygmy resonances can have a significant impact on reaction rates. Reaction rates are important for modeling processes that take place in astrophysical environments and nuclear reactors. Recent results indicate the existence of a significant amount of scissors resonance strength in the photon strength function for nuclei in the actinide region. In order to investigate the extent and persistence of the scissors resonance strength towards lighter nuclei, an experiment was performed utilizing the NaI(Tl) gamma-ray detector array (CACTUS) and silicon particle telescopes (SiRi) at the cyclotron laboratory at the University of Oslo. Particle-gamma coincidences from the 181Ta(d,p)182Ta and 181Ta(d,d’)181Ta reactions were used to measure the nuclear level density and photon strength function of the well-deformed 182Ta and 181Ta systems. From these data (n, ) cross sections were calculated with the Talys reaction code. While there are possible bumps in the photon strength function of 181Ta that may be due to the scissors resonance, it appears to be absent for 182Ta. These results are discussed in the context of nuclear structure and other work done in this and other mass regions.

AFRIKAANSE OPSOMMING : Relatief klein veranderinge aan die algehele vorm van die foton krag funksie soos die sk^er of dwerg resonansies kan beduidende invloed op reaksiesnelhede h^e. Reaksiesnelhede is belangrik vir die modellering van prosesse wat plaasvind in astrofisiese omgewings en kern reaktors. Onlangse resultate dui daarop dat daar ’n beduidende bedrag sk^er resonansie krag in die foton krag funksie vir kerne in die aktinied streek is. Ten einde die omvang en volharding van die sk^er resonansie krag teenoor ligter kerne te bepaal, is ’n eksperiment uitgevoer met behulp van die NaI(Tl) gammastraal-detektor matriks (CACTUS) en silikon deeltjie teleskoop (SiRi) by die siklotron laboratorium aan die Universiteit van Oslo. Deeltjie-gamma toevallighede van die 181Ta(d,p)182Ta en 181Ta(d,d’)181Ta reaksies is gebruik om die kern vlak digtheid en foton krag funksie van die goed vervormde 182Ta en 181Ta stelsels te bepaal. Van hierdie data is (n, ) dwarssnitte bereken met die Talys reaksie kode. Hoewel daar moontlike bewyse vir die sk^er resonansie in die foton krag funksie van 181Ta is, is dit afwesig in 182Ta. Hierdie resultate word bespreek in die konteks van kernstruktuur en ander werk wat in hierdie en ander massa streke gedoen is.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/100282
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