Browsing by Author "Sharpey-Schafer, J. F."

Now showing 1 - 8 of 8
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    Chiral bands in 193Tl
    (Jagiellonian University, 2017-03) Ndayishimye, J.; Lawrie, E. A.; Shirinda, O.; Easton, J. L.; Wyngaardt, S. M.; Bark, R. A.; Bvumbi, S. P.; Dinoko, T. R. S.; Jones, P.; Kheswa, N. Y.; Lawrie, J. J.; Majola, S. N. T.; Masiteng, P. L.; Negi, D.; Orce, J. N.; Papka, P.; Sharpey-Schafer, J. F.; Stankiewicz, M.; Wiedeking, M.
    Since the introduction of chirality in nuclei, the search for chiral candidates in different mass regions has been a hot topic for about two decades. At iThemba LABS, a new chiral symmetry region, the thallium isotopes with mass A ≥ 90 was found. Candidate chiral bands were suggested in 198Tl and then in 194Tl. Most importantly, a comparison of the properties in the chiral partner bands in 194Tl showed that this nucleus is one of the best chiral candidates to date. A search for chiral symmetry in the neighboring thallium isotopes was undertaken. The results from a y-ray spectroscopy study in 193Tl performed at iThemba LABS, South Africa, are discussed.
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    Competition of rotation around the intermediate and long axes in 193Tl
    (American Physical Society, 2019) Ndayishimye, J.; Lawrie, E. A.; Shirinda, O.; Easton, J. L.; Lawrie, J. J.; Wyngaardt, S. M.; Bark, R. A.; Bucher, T. D.; Bvumbi, S. P.; Dinoko, T. R. S.; Jones, P.; Kheswa, N. Y.; Majola, S. N. T.; Masiteng, P. L.; Negi, D.; Orce, J. N.; Sharpey-Schafer, J. F.; Wiedeking, M.
    High-spin states in ¹⁹³Tl were studied and the level scheme was revised and extended including the observation of new rotational bands. A surprising competition between bands built on the same πh9/2⊗νi13/2⁻² nucleon configurations is observed. It is suggested that it is generated by two different rotational modes of this triaxial nucleus: (i) a rotation around the intermediate nuclear axis, producing a pair of chiral symmetry bands, and (ii) a rotation around the long nuclear axis, producing a third band with lower alignment.
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    First candidates for γ vibrational bands built on the [505]11/2– neutron orbital in odd-A Dy isotopes
    (American Physical Society, 2020-05-10) Majola, S. N. T.; Sithole, M. A.; Mdletshe, L.; Hartley, D.; Timar, J.; Nyako, B. M.; Allmond, J. M.; Bark, R. A.; Beausang, C.; Bianco, L.; Bucher, T. D.; Bvumbi, S. P.; Carpenter, M.P.; Chiara, C. J.; Cooper, N.; Cullen, D. M.; Curien, D.; Dinoko, T. S.; Gall, B. J. P.; Garrett, P. E.; Greenlees, P. T.; Hirvonen, J; Jakobsson, U.; Jones, P. M.; Julin, R.; Juutinen, S.; Ketelhut, S.; Kheswa, B. V.; Kondev, F.G.; Korichi, A.; Kulp, W.D.; Lauritsen, T.; Lawrie, E. A.; Makhathini, L.; Masiteng, P. L.; Maqabuka, B.; McCutchan, E.A.; Miller, D.; Miller, S.; Minkova, A.; Msebi, L.; Mthembu, S. H.; Ndayishimye, J.; Nieminen, P.; Ngcobo, P. Z.; Ntshangase, S. S.; Orce, J. N.; Peura, P.; Rahkila, P.; Redon, N.; Riedinger, L. L.; Riley, M. A.; Roux, D. G.; Ruotsalainen, P.; Piot, J.; Saren, J.; Sharpey-Schafer, J. F.; Scholey, C.; Shirinda, O.; Simpson, J.; Sorri, J.; Stefanescu, I.; Stolze, S.; Uusitalo, J.; Wang, X.; Werner, V.; Wood, J.L; Yu, C-H.; Zhu, S.; Zimba, G.
    Rotational structures have been measured using the Jurogam II and GAMMASPHERE arrays at low spin following the 155Gd(α,2n)157Dy and 148Nd(12C, 5n)155Dy reactions at 25 and 65 MeV, respectively. We report high-K bands, which are conjectured to be the first candidates of a Kπ= 2+ γ vibrational band, built on the [505]11/2– neutron orbital, in both odd-A 155, 157Dy isotopes. The coupling of the first excited K=0+ states or the so-called β vibrational bands at 661 and 676 keV in 154Dy and 156Dy to the [505]11/2– orbital, to produce a Kπ=11/2- band, was not observed in both 155Dy and 157Dy, respectively. The implication of these findings on the interpretation of the first excited 0+ states in the core nuclei 154Dy and 156Dy are also discussed.
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    Rotational structures in 196Hg
    (American Physical Society, 2019) Lawrie, J. J.; Lawrie, E. A.; Msezane, B.; Benatar, M.; Fedderke, M.; Mabala, G. K.; Mukherjee, S.; Mullins, S. M.; Mutshena, K. P.; Ncapayi, N. J.; Newman, R. T.; Sharpey-Schafer, J. F.; Smit, F. D.; Vymers, P.
    High spin states in ¹⁹⁶Hg were populated in the ¹⁹⁸Pt(α,6n) reaction at 65 MeV and γ−γ coincidence measurements were performed using the AFRODITE array at iThemba LABS. The level scheme was extended and new rotational bands were observed. A new dipole band was found. The previously reported dipole band was linked to other known states. Excitation energies, spins, and parities of all bands were determined. The bands were assigned nucleon configurations based on cranked shell model calculations.
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    Spectroscopic study of the possibly triaxial transitional nucleus 75Ge
    (American Physical Society, 2018) Niu, C. Y.; Dai, A. C.; Xu, C.; Hua, H.; Zhang, S. Q.; Wang, S. Y.; Bark, R. A.; Meng, Jie; Wang, C. G.; Wu, X. G.; Li, X. Q.; Li, Z. H.; Wyngaardt, S. M.; Zang, H. L.; Chen, Z. Q.; Wu, H. Y.; Xu, F. R.; Ye, Y. L.; Jiang, D. X.; Han, R.; Li, C. G.; Chen, X. C.; Liu, Q.; Feng, J.; Yang, B.; Li, Z. H.; Wang, S.; Sun, D. P.; Liu, C.; Li, Z. Q.; Zhang, N. B.; Guo, R. J.; Li, G. S.; He, C. Y.; Zheng, Y.; Li, C. B.; Chen, Q. M.; Zhong, J.; Zhou, W. K.; Zhu, B. J.; Deng, L. T.; Liu, M. L.; Wang, J. G.; Jones, P.; Lawrie, E. A.; Lawrie, J. J.; Sharpey-Schafer, J. F.; Wiedeking, M.; Majola, S. N. T.; Bucher, T. D.; Dinoko, T.; Magabuka, B.; Makhathini, L.; Mdletshe, L.; Khumalo, N. A.; Shirinda, O.; Sowazi, K.
    The collective structures of 75Ge have been studied for the first time via the 74Ge(α,2p1n) 75Ge fusionevaporation reaction. Two negative-parity bands and one tentative positive-parity band built on the νp1/2, νf5/2, and νg9/2 states, respectively, are established and comparedwith the structures in the neighboringN = 43 isotones. According to the configuration-constrained potential-energy surface calculations, a shape transition from oblate to prolate along the isotopic chain in odd-A Ge isotopes is suggested to occur at 75Ge. The properties of the bands in 75Ge are analyzed in comparison with the triaxial particle rotor model calculations.
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    Spectroscopy of low-spin states in 157Dy : Search for evidence of enhanced octupole correlations
    (American Physical Society, 2019) Majola, S. N. T.; Bark, R. A.; Bianco, L.; Bucher, T. D.; Bvumbi, S. P.; Cullen, D. M.; Garrett, P. E.; Greenlees, P. T.; Hartley, D.; Hirvonen, J.; Jakobsson, U.; Jones, P. M.; Julin, R.; Juutinen, S.; Ketelhut, S.; Kheswa, B. V.; Korichi, A.; Lawrie, E. A.; Masiteng, P. L.; Maqabuka, B.; Mdletshe, L.; Minkova, A.; Ndayishimye, J.; Nieminen, P.; Nyako, B. M.; Peura, P.; Rahkila, P.; Riedinger, L. L.; Riley, M.; Roux, D.; Ruotsalainen, P.; Saren, J.; Sharpey-Schafer, J. F.; Scholey, C.; Shirinda, O.; Sithole, A.; Sorri, J.; Stolze, S.; Timar, J.; Uusitalo, J.; Zimba, G.
    Low-spin states of ¹⁵⁷Dy have been studied using the JUROGAM II array, following the ¹⁵⁵Gd (α, 2n) reaction at a beam energy of 25 MeV. The level scheme of ¹⁵⁷Dy has been expanded with four new bands. Rotational structures built on the [523]5/2⁻ and [402]3/2⁺ neutron orbitals constitute new additions to the level scheme as do many of the inter- and intraband transitions. This manuscript also reports the observation of cross I⁺ →(I–1) ⁻ and I⁻ →(I–1)⁺ E1 dipole transitions interlinking structures built on the [523]5/2⁻ (band 5) and [402]3/2⁺ (band 7) neutron orbitals. These interlacing band structures are interpreted as the bands of parity doublets with simplex quantum number s=–i related to possible octupole correlations.
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    “Stapler” mechanism for a dipole band in 79Se
    (American Physical Society, 2019-10-24) Li, C. G.; Chen, Q. B.; Zhang, S. Q.; Xu, C.; Hua, H.; Wang, S. Y.; Bark, R. A.; Wyngaardt, S. M.; Shi, Z.; Dai, A. C.; Wang, C. G.; Li, X. Q.; Li, Z. H.; Meng, J.; Xu, F. R.; Ye, Y. L.; Jiang, D. X.; Han, R.; Niu, C. Y.; Chen, Z. Q.; Wu, H. Y.; Wang, X.; Luo, D. W.; Wu, C. G.; Wang, S.; Sun, D. P.; Liu, C.; Li, Z. Q.; Sun, B. H.; Jones, P.; Msebi, L.; Sharpey-Schafer, J. F.; Dinoko, T.; Lawrie, E. A.; Ntshangase, S. S.; Kheswa, B. V.; Shirinda, O.; Khumalo, N.; Bucher, T. D.; Malatji, K. L.
    The spectroscopy of 79 Se is studied via the 82 Se(α, α3n)79Se fusion-evaporation reaction. A negative-parity magnetic dipole band in 79Se is established for the first time. Based on the calculations by the self-consistent tilted axis cranking covariant density functional theory, this new dipole band can be classified as a “stapler” band, which has a relatively stable symmetric prolate deformation as a function of rotational frequency. Hence, it is demonstrated that the stapler bands exist not only in the oblate and triaxial nuclei, but also in prolate nuclei. By examining the angular momentum coupling, it is found that the five valence nucleons in the high-j orbitals play a major role in the closing of the stapler.
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    β and γ bands in N = 88 , 90, and 92 isotones investigated with a five-dimensional collective Hamiltonian based on covariant density functional theory : vibrations, shape coexistence, and superdeformation
    (American Physical Society, 2019-06-05) Majola, S. N. T.; Shi, Z.; Song, B. Y.; Li, Z. P.; Zhang, S. Q.; Bark, R. A.; Sharpey-Schafer, J. F.; Aschman, D. G.; Bvumbi, S. P.; Bucher, T. D.; Cullen, D. M.; Dinoko, T. S.; Easton, J. E.; Erasmus, N.; Greenlees, P. T.; Hartley, D. J.; Hirvonen, J.; Korichi, A.; Jakobsson, U.; Jones, P.; Jongile, S.; Julin, R.; Juutinen, S.; Ketelhut, S.; Kheswa, B. V.; Khumalo, N. A.; Lawrie, E. A.; Lawrie, J. J.; Lindsay, R.; Madiba, T. E.; Makhathini, L.; Maliage, S. M.; Maqabuka, B.; Malatji, K. L.; Masiteng, P. L.; Mashita, P. I.; Mdletshe, L.; Minkova, A.; Msebi, L.; Mullins, S. M.; Ndayishimye, J.; Negi, D.; Netshiya, A.; Newman, R.; Ntshangase, S. S.; Ntshodu, R.; Msebi, L.; Mullins, S. M.; Ndayishimye, J.; Negi, D.; Netshiya, A.; Newman, R.; Ntshangase, S. S.; Ntshodu, R.; Nyako, B. M.; Papka, P.; Peura, P.; Rahkila, P.; Riedinger, L. L.; Riley, M. A.; Roux, D. G.; Ruotsalainen, P.; Saren, J. J.; Scholey, C.; Shirinda, O.; Sithole, M. A.; Sorri, J.; Stankiewicz, M.; Stolze, S.; Timar, J.; Uusitalo, J.; Vymers, P. A.; Wiedeking, M.; Zimba, G. L.
    A comprehensive systematic study is made for the collective β and γ bands in even-even isotopes with neutron numbers N = 88 to 92 and proton numbers Z = 62 (Sm) to 70 (Yb). Data, including excitation energies, B(E0) and B(E2) values, and branching ratios from previously published experiments are collated with new data presented for the first time in this study. The experimental data are compared to calculations using a five-dimensional collective Hamiltonian (5DCH) based on the covariant density functional theory (CDFT). A realistic potential in the quadrupole shape parameters V (β,γ ) is determined from potential energy surfaces (PES) calculated using the CDFT. The parameters of the 5DCH are fixed and contained within the CDFT. Overall, a satisfactory agreement is found between the data and the calculations. In line with the energy staggering S(I) of the levels in the 2γ + bands, the potential energy surfaces of the CDFT calculations indicate γ -soft shapes in the N = 88 nuclides, which become γ rigid for N = 90 and N = 92. The nature of the 02 + bands changes with atomic number. In the isotopes of Sm to Dy, they can be understood as β vibrations, but in the Er and Yb isotopes the 02 + bands have wave functions with large components in a triaxial superdeformed minimum. In the vicinity of 152Sm, the present calculations predict a soft potential in the β direction but do not find two coexisting minima. This is reminiscent of 152Sm exhibiting an X(5) behavior. The model also predicts that the 03 + bands are of two-phonon nature, having an energy twice that of the 02 + band. This is in contradiction with the data and implies that other excitation modes must be invoked to explain their origin.