R. Saayman

A study of the93Nb levels populated via the (n, n′ γ) reaction

De-excitation γ-rays from levels in93Nb up to 2203 keV were observed following inelastic neutron scattering at incident energies between 0.6 and 2.575 MeV. The energy level and decay modes of93Nb are deduced. Spin and parity assignments are based on the comparison of the experimental (n, n′) cross sections with calculated cross sections using Hauser-Feshbach theory corrected for level-width fluctuation corrections. The low-lying levels of93Nb have been studied within the framework of the vibration-particle model to account for their energy and spin assignments, as well as the reduced transition probabilities measured in Coulomb excitation experiments.

Shell model calculations on natural parity states in 10≦ A≦14 nuclei

Shell model calculations of natural parity states in the 10≦A≦14 mass region have been performed by assuming an inert4He core with the residual interaction in the 1p shell only. The modified surface delta interaction (MSDI) has been used as an effective two-body interaction. The MSDI parameters as well as the single-particle binding energies have been deduced from a least-squares fit to experimentally known levels in, firstly, the seperate10B,11B-C,12C,13C-N and14N nuclei, and secondly, the whole mass region 10≦A≦14. Multipole moments for ground states and M1 and E2 radiative widths for excited states have been calculated with the resultant wave functions.

A diagnosis of the mathematical and scientific reasoning ability of first-year physics undergraduates

The structure and results of a university physics entry test with 75 multiple-choice items are discussed. It measures students expertise with mathematical tools and formal logical cognitive operations required for the study of physics, and serves as a useful aid to evaluating the academic potential of a particular class, points out specific shortcomings to be rectified and advises individual students on their study choice.

The effect of expansion of the shell model space on the structure of the mass-15 nuclei

The structure of the natural and unnatural parity states of the15N-15O mirror pair, as well as theT=3/2 analogue states of15C, is discussed in terms of shell model calculations with a modified surface delta two-body interaction. The inert core is recomposed from4He to12C and the configuration space is systematically expanded to allow for an increasing number of particle excitations from the 1p into the 2s-1d shell. The relative importance of the 2s 1/2, 1d 5/2 and 1d 3/2 orbitals are evaluated. Some electromagnetic properties of levels are also calculated.

The structure and properties of45Sc at low excitation energies

The spins and electromagnetic properties of levels in45Sc up to 2,352 keV were studied by means of inelastic proton scattering using a 3-parameter coincidence arrangement and Coulomb excitation with3He and4He beams. Relevant experimental results are discussed in terms of the Thankappen-True core-plus-particle model.

Nuclear structure study of51V

The spins and electromagnetic properties of levels up to 3,700 keV in51V were studied by means of inelastic proton scattering. Results are discussed with reference to the many-particle shell model using effective surface delta and realistic Kuo-Brown interactions.

Properties of low-lying levels of39K

The spins and electromagnetic properties of low-lying levels in39K with excitation energy ≦4.127 MeV were studied with the39K(p, p′γ)39K and the36Ar(α, pγ)39K reactions. Experimental results are discussed in terms of shell model calculations with a modified effective surface delta interaction.

Properties of low-lying levels of41K

The atomic nucleus41K was studied with emphysis on the experimental derivation of electromagnetic properties and spin values of low-lying levels with energies ≦3,282 keV. Energy levels, decay properties and mean lifetimes were measured with (p, p′ γ) and (p, p′) reactions at incident proton energies of about 6 MeV. Spin values were deduced from a comparison of results obtained from a Hauser-Feshbach analysis of (p, p′) and (p, p′ γ) reactions and measured transition strengths derived from mixing ratios, lifetimes and decay properties. Experimental results are discussed in terms of shell model calculations with a modified effective surface delta interaction.

Shell-model relationships between negative-parity states of even-massA=30–40 nuclei

Simple relationships between the negative-parityenergy level structures of the even-mass nuclei pairsA=30 and 32, 34 and 40, 34 and 36, 34 and 38, 40 and 38 are established along lines similar to the well-known Pandya transformation between the particle-hole spectrum of40K and the particle-particle spectrum of38Cl. The relationships are generated within the framework of thejj-coupling shell model, using standard Racah algebra, and no assumption is made about the physical nature of the nuclear two-body interaction. Candidates for the 1f7/2 and 2p3/2 multiplets are selected on the basis of their measured spectroscopic strengths inl=3 or 1 single-particle transfer reactions with due allowance for member fragmentation and mixing between the two configurations in terms of the calculation of spectroscopic-strength weighted centroids. The calculated correlated energy spectra are discussed with reference to the results of previous interaction-dependent shell-model calculations, especially those employing the modified surface delta interaction. Consideration is also given to uncertain or ambiguous spin and parity assignments, deduced two-body interaction matrix elements, and the isospinT=0 and 1 and single-particle 1f7/2 and 2p3/2 splittings.