[en] A method for making oxygen targets in a form of lithium carbonate compound is described. Targets were prepared for nuclear physics experiments which required oxygen with a mass greater than 60%. Both natural and isotopic enriched targets of ¹⁸O with thicknesses of less than 1 mg/cm² were produced and characterised by elastic recoil detection analysis and elastic backscattering techniques. The results obtained showed that enriched foils had limited isotopic exchange when exposed to air and good stability with time compared to foils with natural oxygen. (author)

[en] Highly excited and rapidly rotating compound nuclei (CN) produced in fusion-evaporation (FE) reactions can be well investigated by using charged particle spectroscopy. In such hot nuclei, with excitation energies as high as E^*_CN = 80 MeV, the spectral shapes of α particles provide information on the nuclear deformation. We report here on in-plane light charged particle (LCP) - heavy-ion (HI) coincident measurements for the ¹⁶O+²⁸Si reaction. The experiment was carried out at three bombarding energies, E_lab (16 O) = 76 , 96 and 112 MeV with the multidetector array ICARE at the VIVITRON Tandem facility. The Monte Carlo version of the statistical-model code CASCADE, which describes the FE process, has been used to characterize the ⁴⁴Ti CN. A unique set of deformability parameters reproduces well the experimental α spectra to the three bombarding energies. The discrepancies observed for the proton spectra are still to be explained. (author)

No abstract available

[en] The excitation functions of ¹²C(α,γ)¹⁶O and ²²Ne(α,n)²⁵Mg have been determined with a yet unequaled experimental sensitivity of 10^-11 b. From γ-angular distributions the S_E1-and S_E2-factors for ¹²C(α,γ)¹⁶O have been deduced and extrapolated into the range of helium burning temperatures using the R-matrix method. An improved reaction rate has been calculated: N_A<σν>=(7.9±2.5)x10^-15cm³(mols)^-1 at T₉ = 0.2. For a more precise extrapolation the excitation function has to be measured with better statistics. Therefore a new experiment on ¹²C(α,γ)¹⁶O with a better suited setup has been started recently. The accuracy of the ²²Ne(α,n)²⁵Mg reaction rate could be improved considerably compared to previous compilations: N_A<σν> = (0.88_-0.3^+2.6) x 10^-16cm³(mols)^-1 at T₉ = 0.2

[en] A great deal of research work has been undertaken in the α-clustering study since the pioneering discovery, half a century ago, of ¹²C + ¹²C molecular resonances. Our knowledge in the physics of nuclear molecules has increased considerably and nuclear clustering remains one of the most fruitful domains of nuclear physics, facing some of the greatest challenges and opportunities in the years ahead. In this work, the occurrence of '' exotic '' shapes in light N = Z α-like nuclei is investigated. Various approaches of superdeformed and hyperdeformed bands associated with quasimolecular resonant structures are presented. Results on clustering aspects are also discussed for light neutron-rich oxygen isotopes. (authors)

[en] A complete kinematics measurement was performed using the ⁶Li(³He,t) charge exchange reaction to populate ⁶Be at E_lab = 50 MeV. Decay mode of the ground and first excited states were studied through the analysis of the energy and angular distributions of the break-up particles in the ⁶Be center of mass frame. Two-body decay is observed above the first excited state but not firmly assigned to a ⁶Be resonant state. Experimental challenges regarding the identification of true ⁶Be events in the excitation energy region 5 < E_x < 20 MeV are discussed. (author)

[en] The ⁴⁶Ti* compound nucleus, as populated by the fusion-evaporation reaction ²⁷Al + ¹⁹F at the bombarding energy of 144 MeV, has been investigated by charged particle spectroscopy using the multidetector array ICARE at the VIVITRON tandem facility of the IReS (Strasbourg). The light charged particles have been measured in coincidence with evaporation residues. The CACARIZO code, a Monte Carlo implementation of the statistical model code CASCADE, has been used to calculate the spectral shapes of evaporated α-particles which are compared with the experimental spectra. This comparison indicates the possible signature of large deformations of the compound nucleus. (author)

[en] Charged particle and γ-decays in light α-like nuclei are investigated for "2"4Mg +"1"2C. Various theoretical predictions for the occurrence of superdeformed and hyperdeformed bands associated with resonance structures with low spin are presented. The inverse kinematics reaction "2"4Mg +"1"2C is studied at E_l_a_b("2"4Mg) = 130 MeV. Exclusive data were collected with the Binary Reaction Spectrometer in coincidence with EUROBALL IV installed at the VIVITRON Tandem facility at Strasbourg. Specific structures with large deformation were selectively populated in binary reactions and their associated γ-decays studied. Coincident events from α-transfer channels were selected by choosing the excitation energy or the entry point via the two-body Q-values. The analysis of the binary reaction channels is presented with a particular emphasis on "2"0Ne-γ and "1"6O-γ coincidences. (author)

[en] The ⁸⁶Kr+²³⁸U reaction has been studied at krypton beam energies about 30 MeV above the Coulomb barrier. Reaction products were detected by an array of 32 photovoltaic cells coupled to the AFRODITE γ-ray detector array at iThemba LABS. A symmetric fission component has been observed at about 600 MeV total kinetic energy. This could possibly be due to fusion-fission with a cross section of 35±20 mb

[en] Full text: The very strong attractive forces between nucleons in a nucleus cause the protons and neutrons each to pair off into time reversed orbits with magnetic quantum numbers 𝑚 and –𝑚. Thus the angular momentum of each nucleon is opposite to its pairing partner, giving zero angular momentum for the pair. In nuclei with even numbers of both protons and neutrons (e-e) all the nucleons are paired off and the lowest energy state, the “ground” state, has zero angular momentum and is spherically symmetric. This is written 0₁⁺ where ₁ is for the first state and ⁺ is the parity. Odd nuclei, e-e nuclei with an extra proton or neutron, then have the last nucleon in a “single particle” state outside the e-e core. The properties of this state depend critically on the shape of the nucleus. Reactions where protons are stripped off the beam nucleus, so that the outgoing particle is a neutron, are difficult to carry out. In particular it is especially challenging to obtain sufficient neutron energy resolution. Examples of these neutron emitting direct reactions are (d,n) and (³He,n) which donate one and two protons to the target nucleus respectively. One proton stripping can be made with the (³He,d) reaction, but two proton stripping requires reactions using heavy ions such as (¹⁶O,¹⁴C) and very good resolutions are still difficult to achieve. The (³He,xn) reaction has been applied, using the detection of the neutrons, to search for excited 0⁺ states in the residual nucleus. Excellent energy resolution is achieved by the use of γ-ray detection. The Sn isotopes (Z=50) are particularly interesting as their stable isotopes have their neutrons in the middle of the N=50-82 shell but have a closed proton shell at Z=50. This proton shell closure keeps the lowest energy levels in these nuclei spherical. But as soon as the proton closed shell is broken by proton excitation, the neutron orbitals drive the nuclei to become deformed. Experimental results from these first high resolution measurements of L=0 two proton stripping to both spherical and deformed nuclei across the Z=50 proton shell closure have been obtained and will be presented. There is a wealth of new experiments to be carried out using this innovative technique at iThemba LABS for the study of 0⁺ states using such reactions and new approaches. iThemba LABS is currently starting an electron spectroscopy group with an aim to build and have access to spectrometers and collaborations. New ideas and status of the work will be presented. (author)