Determining the spectroscopic quadrupole moment of the first 2+ state in 36Ar

Abstract

A series of reorientation-effect Coulomb-excitation experiments were carried out at iThemba LABS from April to May 2016. Enriched ion beams of 􀬸􀬴Ar, 􀬷􀬺Ar and 􀬷􀬶S were bombarded at safe energies, well below the Coulomb barrier, onto a heavy􀬵􀬽􀬸Pt target with thickness 1mg/cm2. The three experiments were performed to determine the spectroscopic or static quadrupole moment 𝑄􀯦, of the first excitation 2􀬵 􀬾 in these nuclei in order to shed light on the zip-zap of nuclear shapes found at the end of the sd shell. This thesis will be dealing with the particular case of 􀬷􀬺Ar, accelerated at a safe bombarding energy of 134.2 MeV. For this purpose, a particle-gamma coincidence experiment has been carried out using the AFRODITE array  composed of 8 high-purity germanium clover detectors  to detect the de-exciting gamma energies, coupled to a double-sided CD-type S3 silicon detector at backward angles  composed of 32 sectors and 24 rings  to detect the scattering particles. A new optimised sorting code has been developed which included fast computing processing, non-Doppler (194Pt) and Doppler correction (36Ar), add-back, and energysharing, particle and time tagging conditions. The peaks of interests in the spectra were analysed using the Coulombexcitation code GOSIA. Using the normalization method, a more precise determination of 𝑄􀯦􁈺2􀬵 􀬾􁈻 􀵌 􀵅0.09􁈺3􁈻 eb has been accomplished.