The nature and structure of high-energy resonance states in ${}^8\mathrm{Be}$, located just below and above the $p+{}^7\mathrm{Li}$ threshold, are investigated in detail. A microscopic many-cluster and many-channel model is employed to study the formation of these resonances. This model includes three distinct three-cluster configurations: ${}^4\mathrm{He}+{}^3\mathrm{H}+p$, ${}^4\mathrm{He}+{}^3\mathrm{He}+n$, and ${}^4\mathrm{He}+d+d$, enabling a comprehensive treatment of all major binary decay channels of ${}^8\mathrm{Be}$, namely ${}^4\mathrm{He}+{}^4\mathrm{He}$, $p+{}^7\mathrm{Li}$, $n+{}^7\mathrm{Be}$, and $d+{}^6\mathrm{Li}$. The primary focus of our analysis is the structure and dominant decay channels of the twin $1^{+}$, $2^{+}$, $3^{+}$, and $4^{+}$ resonance states. Additionally, we propose and implement a model to clarify how the $2^{+}$ resonance states lying below the $p+{}^7\mathrm{Li}$ threshold are formed. We demonstrate that these resonances are Feshbach-type states arising due to coupling of the open ${}^4\mathrm{He}+{}^4\mathrm{He}$ channel with the closed channels $p+{}^7\mathrm{Li}$, $n+{}^7\mathrm{Be}$, and $d+{}^6\mathrm{Li}$ at these energies. Overall, the present approach provides a realistic description of the experimentally observed resonance spectrum near the ${}^7\mathrm{Li}+p$ decay threshold, including negative-parity states $1^{-}$ and $2^{-}$. Our results are consistent with other microscopic calculations but offer more detailed insight into the internal structure and decay pathways of these resonances.

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• Big bang nucleosynthesis
• Cluster models
• Energy levels
• Nuclear astrophysics
• Nuclear reactions
• Nuclear structure & decays