>Magister Scientiae - MSc / In this work we have determined the spectroscopic or static quadrupole moment
of the rst excited state (QS (2+1) lying at 2230.6 keV in 32S using the reorientation
e ect. The Coulomb-excitation experiment at safe bombarding energies
was performed at iThemba LABS's AFRODITE vault, where 32S beams at
120.3 MeV were bombarded onto a 194Pt target of 1 mg/cm2 thickness. The
beam energy has been chosen such that the separation between nuclear surfaces
is greater than 6.5 fm at all scattering angles, in order to avoid nuclear
interactions. A double-sided CD-type S3 silicon detector, with 24 rings and
32 sectors, has been placed upstream (at backward angles) to detect the scattered
particles. Gamma rays have been detected with the AFRODITE clover
array. This particle-gamma coincidence experiment allows for an angular distribution
and Doppler correction of the gamma rays emitted at 9% the speed
of light. The cross sections (or gamma-ray integrated yields) measured as a
function of scattering angle at backward angles are sensitive to second-order
perturbation e ects in Coulomb excitation, i.e., diagonal matrix elements which
are directly related to the spectroscopic quadrupole moment. The gamma-ray
integrated yields obtained from this experiment are compared with the GOSIA
simulations, yielding a new measurement of QS (2+1) = 0:10 0:7 eb, which
corresponds to a prolate shape in the intrinsic frame of the nucleus. The uncertainty
of this measurement is limited by statistics. This result agrees with
previous measurements and con rms the zig zag of shapes at the end of the
sd shell when approaching the doubly-magic nucleus 40Ca. Nonetheless, the
mystery continues as a prolate shape for the rst 2+ disagrees with modern
theoretical mean- eld calculations and the pairing coupling model.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uwc/oai:etd.uwc.ac.za:11394/7334 |
| Date | January 2019 |
| Creators | Mavela, Lihleli |
| Contributors | Orce, J. N. |
| Publisher | University of the Western Cape |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Rights | University of the Western Cape |
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