Search

Measurements of the angular correlation function W(θ) were performed with the iThemba LABS segmented clover detector. A set of measurements with radioactive sources and irradiated targets was carried out to check the performance of the detector. At short detector-to-source distance, the detector covers the whole range of angles needed for precise angular correlation measurements. Preliminary results show that our detector can measure precisely angular correlation functions, including for transitions with large multipole order such as E3, M4, E4, etc., and deliver mixing ratios of mixed magnetic and electric nature. [ABSTRACT FROM AUTHOR]

Measurements of the proportional crosstalk were performed for the iThemba LABS segmented clover detector. More than 1000 crosstalk parameters were determined and a crosstalk correction algorithm was implemented successfully. [ABSTRACT FROM AUTHOR]

A γ-spectroscopy study to search for chirality in 193Tl was conducted. Three negative-parity bands with close excitation energies and almost equal B(M1)/B(E2) values were identified. These bands were associated with the same πh9=2 ⊗vi13=2² configuration which is suitable for chiral symmetry. Analysis of the properties of these bands suggested that one or two chiral systems are formed in 193Tl. [ABSTRACT FROM AUTHOR]

The 152Sm(16O, 5n)163Yb reaction at a beam energy of 93 MeV was used to study the excited states of 163Yb with the AFRODITE γ -ray spectrometer at iThemba LABS. The level scheme of 163Yb has been extended and new rotational bands established. The band based on the ground-state has been extended from a spin of 11/2- to spin 43/2-. A high-K band based on the neutron [505]11/2- Nilsson orbital has been observed and is reported for the first time in this work. Additional new states in 163Yb were observed which all decay to the yrast band. Some of these states are placed in a sequence which is conjectured to be a γ band involving a coupling with the i13/2[642]5/2+ neutron orbital. The band structures are discussed with reference to Cranked Shell Model (CSM) calculations and a systematic comparison with the neighbouring nuclei. [ABSTRACT FROM AUTHOR]

We review the current experimental data on collective structures within the pairing gap of even-even deformed nuclei, with emphasis on nuclei near mass number A∼150. The essential physics that determines the characteristics of the first excited 0+ (02+) state in these nuclei has been in dispute for several decades. Interpretation of these states in terms of surface β quadrupole vibrations has often been challenged. We examine the role that configuration dependent pairing can play in these levels particularly at the onset of deformation as major shells fill. In all deformed nuclei rotational bands are found experimentally, starting at a state with spin 2+ with excitation energies near the middle of the pairing gap. These rotational bands, with quantum number Kπ=2+, are usually referred to as γ bands and have been identified with quadrupole surface vibrations in the plane perpendicular to the major axis of deformation. However Kπ=2+ bands can also arise due to the breaking of axial symmetry of the quadrupole shape. We discuss data that can help with these different interpretations. [ABSTRACT FROM AUTHOR]

The structure of the low-lying positive parity bands in 162Yb has been studied at iThemba LABS, using the 150Sm(16O,4n)162Yb fusion-evaporation reaction. A band built on the first excited 02+ state has been identified for the first time. In addition, we report new rotational levels that form the band structures of both the odd and even spin components of the γ-vibrational band. The first excited 02+ band and the even spin members of the γ-vibrational band exhibit a Landau-Zenner crossing. This crossing demonstrates that the significant signature splitting between the odd and even spin members of the γ band is contributed to by band mixing. [ABSTRACT FROM AUTHOR]

High-spin states in 193Tl were studied and the level scheme was revised and extended including the observation of new rotational bands. A surprising competition between bands built on the same πh9/2⊗νi13/2-2 nucleon configurations is observed. It is suggested that it is generated by two different rotational modes of this triaxial nucleus: (i) a rotation around the intermediate nuclear axis, producing a pair of chiral symmetry bands, and (ii) a rotation around the long nuclear axis, producing a third band with lower alignment. [ABSTRACT FROM AUTHOR]