Browsing by Author "Mira, J. P."

Now showing 1 - 4 of 4
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    Deformation dependence of the isovector giant dipole resonance : the neodymium isotopic chain revisited
    (Elsevier, 2018) Donaldson, L. M.; Bertulani, C. A.; Carter, J.; Nesterenko, V. O.; Von Neumann-Cosel, P.; Neveling, R.; Ponomarev, V. Yu; Reinhard, P. G.; Usman, I. T.; Adsley, P.; Brummer, J. W.; Buthelezi, E. Z.; Cooper, G. R. J.; Fearick, R. W.; Fortsch, S. V.; Fujita, H.; Fujita, Y.; Jingo, M.; Kleinig, W.; Kureba, C. O.; Kvasil, J.; Latif, M.; Li, K. C. W.; Mira, J. P.; Nemulodi, F.; Papka, P.; Pellegri, L.; Pietralla, N.; Richter, A.; Sideras-Haddad, E.; Smit, F. D.; Steyn, G. F.; Swartz, J. A.; Tamii, A.
    Proton inelastic scattering experiments at energy Ep=200MeV and a spectrometer scattering angle of 0° were performed on 144,146,148,150Nd and 152Sm exciting the IsoVector Giant Dipole Resonance (IVGDR). Comparison with results from photo-absorption experiments reveals a shift of resonance maxima towards higher energies for vibrational and transitional nuclei. The extracted photo-absorption cross sections in the most deformed nuclei, 150Nd and 152Sm, exhibit a pronounced asymmetry rather than a distinct double-hump structure expected as a signature of K-splitting. This behaviour may be related to the proximity of these nuclei to the critical point of the phase shape transition from vibrators to rotors with a soft quadrupole deformation potential. Self-consistent random-phase approximation (RPA) calculations using the SLy6 Skyrme force provide a relevant description of the IVGDR shapes deduced from the present data.
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    Indirect study of the stellar ³⁴ Ar(α,p) ³⁷K reaction rate through ⁴⁰Ca(p,t) ³⁸Ca reaction measurements
    (American Physical Society, 2017) Long, A. M.; Adachi, T.; Beard, M.; Berg, G. P. A.; Buthelezi, Z.; Carter, J.; Couder, M.; deBoer, R. J.; Fearick, R. W.; Fortsch, S. V.; Gorres, J.; Mira, J. P.; Murray, S. H. T.; Neveling, R.; Papka, P.; Smit, F. D.; Sideras-Haddad, E.; Swartz, J. A.; Talwar, R.; Usman, I. T.; Wiescher, M.; Van Zyl, J. J.; Volya, A.
    The ³⁴Ar(α,p)³⁷K reaction is believed to be one of the last in a sequence of (α,p) and (p,γ) reactions within the Tz=−1, sd-shell nuclei, known as the αp-process. This process is expected to influence the shape and rise times of luminosity curves coming from type I x-ray bursts (XRBs). With very little experimental information known on many of the reactions within the αp-process, stellar rates are calculated using a statistical model, such as Hauser-Feshbach. Questions on the applicability of a Hauser-Feshbach model for the ³⁴Ar(α,p) ³⁷K reaction arise due to level density considerations in the compound nucleus, 38Ca. We have performed high energy-resolution forward-angle ⁴⁰Ca(p,t)³⁸Ca measurements with the K=600 spectrograph at iThemba LABS in order to identify levels above the α-threshold in ³⁸Ca. States identified in this work were then used to determine the ³⁴Ar(α,p)³⁷K reaction rate based on a narrow-resonance formalism. Comparisons are made to two standard Hauser-Feshbach model predicted rates at XRB temperatures.
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    Search for highly excited states in ²⁸Si
    (IOP Publishing, 2017) Montanari, D.; Courtin, S.; Jenkins, D. G.; Diget, C.; Yavuzkanat, N.; Neveling, R.; Mira, J. P.; Nemulodi, F.; Smit, F. D.; Usman, I.; Papka, P.; Swartz, J. A.; Van Zyl, J. J.; Orce, N.
    The theoretical and experimental determination of superdeformed states in nuclei in the mass region A≤40 has been since a long time one of the major challenges of nuclear structure studies. Despite the considerable experimental and theoretical work dedicated to this topic, up to now superdeformed bands have been found in only two nuclei, ³⁶Ar and ⁴⁰Ca. While the experimental signature of the superdeformed nature of those states is irrefutable, their theoretical interpretation is still uncertain. In particular, it is not clear whether clusterisation is responsible of the onset of superdeformation. For this reason, we wanted to investigate an even lighter system, ²⁸Si, where a number of theoretical calculations predict the presence of superdeformation as an effect of the cluster structure of the nucleus.
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    Wavelet signatures of K-splitting of the Isoscalar Giant Quadrupole Resonance in deformed nuclei from high-resolution (p, p ) scattering off ¹⁴⁶,¹⁴⁸,¹⁵⁰Nd
    (Elsevier, 2018) Kureba, C. O.; Buthelezi, Z.; Carter, J.; Cooper, G. R. J.; Fearick, R. W.; Fortsch, S. V.; Jingo, M.; Kleinig, W.; Krugmann, A.; Krumbolz, A. M.; Kvasil, J.; Mabiala, Justin; Mira, J. P.; Nesterenko, V. O.; Von Neumann-Cosel, P.; Neveling, R.; Papka, P.; Reinhard, P. G.; Richter, A.; Sideras-Haddad, E.; Smit, F. D.; Steync, G. F.; Swartz, J. A.; Tamii, A.; Usman, I. T.
    The phenomenon of fine structure of the Isoscalar Giant Quadrupole Resonance (ISGQR) has been studied with high energy-resolution proton inelastic scattering at iThemba LABS in the chain of stable even-mass Nd isotopes covering the transition from spherical to deformed ground states. Awavelet analysis of the background-subtracted spectra in the deformed 146,148,150Nd isotopes reveals characteristic scales in correspondence with scales obtained from a Skyrme RPA calculation using the SVmas10 parameterization. Asemblance analysis shows that these scales arise from the energy shift between the main fragments of the K=0, 1and K=2components.