Browsing by Author "Adsley, P."

Now showing 1 - 8 of 8
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    Characterization of the proposed 4−α cluster state candidate in ¹⁶O
    (American Physical Society, 2017) Li, K. C. W.; Neveling, R.; Adsley, P.; Papka, P.; Smit, F. D.; Brummer, J. W.; Diget, C. Aa.; Freer, M.; Harakeh, M. N.; Kokalova, Tz.; Nemulodi, F.; Pellegri, L.; Rebeiro, B.; Swartz, J. A.; Triambak, S.; Van Zyl, J. J.; Wheldon, C.
    The 0¹⁶O(α,α′) reaction was studied at θlab=0∘ at an incident energy of Elab=200 MeV using the K600 magnetic spectrometer at iThemba LABS. Proton decay and α decay from the natural parity states were observed in a large-acceptance silicon strip detector array at backward angles. The coincident charged-particle measurements were used to characterize the decay channels of the 0⁺₆ state in ¹⁶O located at Ex=15.097(5) MeV. This state is identified by several theoretical cluster calculations to be a good candidate for the 4−α cluster state. The results of this work suggest the presence of a previously unidentified resonance at Ex≈15 MeV that does not exhibit a 0⁺ character. This unresolved resonance may have contaminated previous observations of the 0⁺₆ state.
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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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    Effectiveness of using a magnetic spectrograph with the Trojan Horse method
    (IOP Publishing, 2018) Manwell, S.; Parikh, A.; Chen, A. A.; De Sereville, N.; Adsley, P.; Irvine, D.; Hammache, F.; Stefan, I.; Longland, R. F.; Tomlinson, J.; Morfuace, P.; Le Crom, B.
    The Trojan Horse method relies on performing reactions in a specific kinematic phase space that maximizes contributions of a quasi-free reaction mechanism. The hallmark of this method is that the incident particle can be accelerated to high enough energies to overcome the Coulomb barrier of the target, but once inside the target nucleus the relative motion of the clustered nuclei allows the reaction of interest to proceed at energies below this Coulomb Barrier. This method allows the experimentalist to probe reactions that have significance in astrophysics at low reaction energies that would otherwise be impossible due to the vanishing cross section. Traditionally the Trojan Horse method has been applied with the use of silicon detectors to observe the reaction products. In this study we apply the Trojan Horse method to a well studied reaction to examine the potential benefits of using a splitpole magnetic spectrograph to detect one of the reaction products. We have measure the three body 7Li(d,αn)α reaction to constrain the energy 7Li(d,α)α cross section. Measurements were first made using two silicon detectors, and then by replacing one detector with the magnetic spectrograph. The experimental design, limitations, and early results are discussed.
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    High-resolution study of levels in the astrophysically important nucleus 26Mg and resulting updated level assignments
    (American Physical Society, 2018) Adsley, P.; Brummer, J. W.; Faestermann, T.; Faestermann, T.; Fox, S. P.; Hammache, F.; Hertenberger, R.; Meyer, A.; Neveling, R.; Seiler, D.; De Sereville, N.; Wirth, H. F.
    Background: The 22Ne(α,n)25Mg reaction is an important source of neutrons for the s-process. Direct measurement of this reaction and the competing 22Ne(α,γ)26Mg reaction are challenging due to the gaseous nature of both reactants, the low cross section and the experimental challenges of detecting neutrons and high-energy γ rays. Detailed knowledge of the resonance properties enables the rates to be constrained for s-process models. Purpose: Previous experimental studies have demonstrated a lack of agreement in both the number and excitation energy of levels in 26Mg. To try to resolve the disagreement between different experiments, proton and deuteron inelastic scattering from 26Mg have been used to identify excited states. Method: Proton and deuteron beams from the tandem accelerator at the Maier-Leibnitz Laboratorium at Garching, Munich, were incident upon enriched 26MgO targets. Scattered particles were momentum-analyzed in the Q3D magnetic spectrograph and detected at the focal plane. Results: Reassignments of states around Ex=10.8–10.83 MeV in 26Mg suggested in previous works have been confirmed. In addition, new states in 26Mg have been observed, two below and two above the neutron threshold. Up to six additional states above the neutron threshold may have been observed compared to experimental studies of neutron reactions on 25Mg, but some or all of these states may be due to 24Mg contamination in the target. Finally, inconsistencies between measured resonance strengths and some previously accepted Jπ assignments of excited 26Mg states have been noted. Conclusion: There are still a large number of nuclear properties in 26Mg that have yet to be determined and levels that are, at present, not included in calculations of the reaction rates. In addition, some inconsistencies between existing nuclear data exist that must be resolved in order for the reaction rates to be properly calculated.
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    Nuclear structure studies relevant to ¹³⁶Xe ββ decay
    (IOP Publishing, 2018) Rebeiro, B. M.; Triambak, S.; Garrett, P. E.; Lindsay, R.; Adsley, P.; Ball, G. C.; Bildstein, V.; Burbadge, C.; Diaz-Varela, A.; Faestermann, T.; Hertenberger, R.; Jigmeddorj, B.; Kamil, M.; Leach, K. G.; Mabika, P. Z.; Nzobadila, J. C.; Orce, J. N.; Radich, A. J.; Rand, E.; Wirth, H. F.
    In these proceedings we briefly discuss preliminary results from ¹³⁸Ba(d, α) and ¹³⁸Ba(p, t) reactions performed using the Q3D magentic spectrometer at the Maier-Leibnitz- Laboratorium (MLL) tandem accelerator facility in Garching, Germany. Our results aim to provide useful spectroscopic information for the calculation of the ¹³⁶Xe →¹³⁶ Ba double beta decay matrix elements.
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    Second T = 3/2 state in 9B and the isobaric multiplet mass equation
    (American Physical Society, 2018) Mukwevho, N. J.; Rebeiro, B. M.; Marin-Lambarri, D. J.; Triambak, S.; Adsley, P.; Kheswa, N. Y.; Neveling, R.; Pellegri, L.; Pesudo, V.; Smit, F. D.; Akakpo, E. H.; Brümmer, J. W.; Jongile, S.; Kamil, M.; Mabika, P. Z.; Nemulodi, F.; Orce, J. N.; Papka, P.; Steyn, G. F.; Yahia-Cherif, W.
    Recent high-precision mass measurements and shell-model calculations [M. Brodeur et al., Phys. Rev. Lett. 108, 212501 (2012)] have challenged a longstanding explanation for the requirement of a cubic isobaric multiplet mass equation for the lowest A=9 isospin quartet. The conclusions relied upon the choice of the excitation energy for the second T=3/2 state in 9B, which had two conflicting measurements prior to this work. We remeasured the energy of the state using the 9Be(3He,t) reaction and significantly disagree with the most recent measurement. Our result supports the contention that continuum coupling in the most proton-rich member of the quartet is not the predominant reason for the large cubic term required for A=9 nuclei.
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    Spectroscopy of low lying states in 136Cs
    (IOP Publishing, 2016) Rebeiro, B.; Triambak, S.; Lindsay, R.; Adsley, P.; Burbadge, C.; Ball, G.; Bildstein, V.; Faestermann, T.; Garrett, P. E.; Hertenberger, R.; Radich, A.; Rand, E.; Varela, A.; Wirth, H.-F.
    The low-lying excited states in 136Cs relevant to the double beta decay of 136Xe were studied via a 138Ba(d, α)136Cs transfer reaction with a high resolution magnetic spectrometer. Preliminary results from the experiment are presented.
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    α clustering in ²⁸Si probed through the identification of high-lying 0⁺ states
    (American Physical Society, 2017) Adsley, P.; Jenkins, D. G.; Cseh, J.; Dimitriova, S. S.; Brummer, J. W.; Li, K. C. W.; Marin-Lambarri, D. J.; Lukyanov, K.; Kheswa, N. Y.; Neveling, R.; Papka, P.; Pellegri, L.; Pesudo, V.; Pool, L. C.; Riczu, G.; Smit, F. D.; Van Zyl, J. J.; Zemlyanaya, E.
    Background: Aspects of the nuclear structure of light α-conjugate nuclei have long been associated with nuclear clustering based on α particles and heavier α-conjugate systems such as ¹²C and ¹⁶O. Such structures are associated with strong deformation corresponding to superdeformed or even hyperdeformed bands. Superdeformed bands have been identified in ⁴⁰Ca and neighboring nuclei and find good description within shell model, mean-field, and α-cluster models. The utility of the α-cluster description may be probed further by extending such studies to more challenging cases comprising lighter α-conjugate nuclei such as ²⁴Mg, ²⁸Si, and ³²S. Purpose: The purpose of this study is to look for the number and energy of isoscalar 0⁺ states in ²⁸Si. These states are the potential bandheads for superdeformed bands in ²⁸Si corresponding to the exotic structures of ²⁸Si. Of particular interest is locating the 0⁺ bandhead of the previously identified superdeformed band in ²⁸Si. Methods: α-particle inelastic scattering from a natSi target at very forward angles including 0∘ has been performed at the iThemba Laboratory for Accelerator-Based Sciences in South Africa. Scattered particles corresponding to the excitation energy region of 6 to 14 MeV were momentum-analysed in the K600 magnetic spectrometer and detected at the focal plane using two multiwire drift chambers and two plastic scintillators. Results: Several 0⁺ states have been identified above 9 MeV in ²⁸Si. A newly identified 9.71 MeV 0⁺ state is a strong candidate for the bandhead of the previously discussed superdeformed band. The multichannel dynamical symmetry of the semimicroscopic algebraic model predicts the spectrum of the excited 0⁺ states. The theoretical prediction is in good agreement with the experimental finding, supporting the assignment of the 9.71-MeV state as the bandhead of a superdeformed band. Conclusion: Excited isoscalar 0⁺ states in ²⁸Si have been identified. The number of states observed in the present experiment shows good agreement with the prediction of the multichannel dynamical symmetry.