Highly excited high spin states in ²⁸Si populated through the ¹²C(²⁰Ne, α) reaction

High spin states at 12.0-17.6 MeV in ²⁸Si excited through the ¹²C(²⁰Ne, α) reaction have been investigated with a particle-particle angular correlation method. New spin-parity assignments ranging from 3^- to 10⁺ have been made, some of which are classified into an excited prolate band reported previously. Most states in this energy region are found to decay both by alpha and proton emission. Specifically, a new 6⁺ state found at 12.80 MeV is identified to be the lowest excited state whch has a large fraction of g _{9 2} component. This is also supported by a successful reanalysis of the ²⁷Al(α, t)²⁸Si reaction at 65 MeV by a DWBA calculation assuming g _{9 2} transfer. These high-lying states also are discussed in terms of coexistence of oblate and prolate shape bands in ²⁸Si. The particle decay property of these states in ²⁸Si is also discussed comparatively with that in ³²S.