Coulomb excitation of the 2+ state in 14C and the quadrupole deformation of states in 194Pt

Brits, Christiaan Petrus (2019-12)

Thesis (PhD)--Stellenbosch University, 2019.

Thesis

ENGLISH ABSTRACT: The safe Coulomb excitation experiment of 14C and 194Pt which took place at Florida State University took advantage of the unique beam capabilities, the availability of highefficiency large volume LaBr3(Ce) detectors and the S3 double sided silicon strip detector. Using the advantageous experimental environment the B(E2: 2+1 ! 0+1 ) value of the firstexcited 2+1 state of 14C and the quadrupole deformation of states in 194Pt are investigated. B(E2: 2+1 ! 0+1 ) values of neutron-rich even-even C isotopes have been reported up to 20C and provide important information on the evolution of the underlying structural mechanism towards the drip line. They also provide critical constraints for theoretical models as is the case for the experimentally determined B(E2: 2+1 ! 0+1 ) value for 14C which exhibits persistent inconsistencies with that obtained from theoretical models. The B(E2: 2+1 ! 0+1 ) value in 14C cannot be reproduced by theoretical models making it indispensable to enhance our theoretical understanding of the C isotopic chain in general. The 2+1 state was not observed in the particle- data, which may indicate that 14C undergoes single-particle excitation and has a smaller B(E2: 2+1 ! 0+1 ) value than previously thought. The A 190 region is very interesting since it has oblate, prolate, -soft and spherical shaped nuclei. It is predicted that Pt evolves from prolate deformed 180􀀀186Pt to -soft 188Pt and triaxial 190Pt to oblate 192􀀀198Pt and finally to spherical 204Pt. From this work, the quadrupole deformation of the 0+1 , 2+1 , 4+1 , 2+2 , 4+2 states are successfully measured with increased accuracy. Additionally it is determined that 194Pt is triaxial oblate which supports the theoretical prediction of the shape evolution in Pt.

AFRIKAANSE OPSOMMING: Die veilige Coulomb-eksitasie eksperiment van 14C en 194Pt aan die Florida State University het voordeel getrek uit die unieke vermoëns, die beskikbaarheid van hoë-doeltreffend groot volume LaBr3(Ce) detektors en die S3 silikon strook detektor. In die voordelige eksperimentele omgewing word ’n poging aangewend om die B(E2: 2+1 ! 0+1 ) van 14C te meet en die vierhoekige vervorming van vlakke in 194Pt. B(E2: 2+1 ! 0+1 ) waardes van neutronryke gelyke C isotope is aangemeld tot 20C en verskaf belangrike inligting oor die evolusie van die onderliggende strukturele meganisme teenoor die druplyn en kritiese beperkings vir teoretiese modelle. Die eksperimentele vasgestelde B(E2: 2+1 ! 0+1 ) waarde vir 14C vertoon egter volgehoue teenstrydighede met die waardes verkry uit teoretiese modelle. Die waarde van B(E2: 2+1 ! 0+1 ) in 14C kan nie gereproduseer word deur teoretiese modelle nie, wat dit onontbeerlik maak om ons teoretiese begrip van C isotopiese ketting in die algemeen te verbeter. Die 2+1 staat is nie waargeneem in die deeltjie- data nie, wat die moontlikheid uitwys van ’n enkel-deeltjie opwekking en ’n kleiner B(E2: 2+1 ! 0+1 ) waarde as verwag. Die A 190 streek is baie interessant aangesien dit afgeplatte, prolate, -sag en sferiese kerne bevat. Daar word voorspel dat Pt ontwikkel van die vervormde 180􀀀186Pt tot -sag 188Pt en triaksiaal 190Pt na afgeplatte 192􀀀198Pt tot uiteindelike spheriese 204Pt. Uit hierdie werk is die vierhoekige vervorming van die 0+1 , 2+1 , 4+1 , 2+2 , 4+2 state suksesvol gemeet met verhoogde akkuraatheid. Daarbenewens word dit vasgestel dat 194Pt triaksiaal afgeplat is wat die teoretiese voorspelling van Pt evolusie ondersteun.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/107055
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