α clustering in ²⁸Si probed through the identification of high-lying 0⁺ states

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. (2017)

CITATION: Adsley, P., et al. 2017. α clustering in ²⁸Si probed through the identification of high-lying 0⁺ states. Physical Review C, 95(2):1-8, doi:10.1103/PhysRevC.95.024319.

The original publication is available at https://journals.aps.org/prc

Article

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.

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