Browsing by Author "Fortsch, S. V."

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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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    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.