Existence of core excited 8Be* = α + α* cluster structure in α + α scattering.

We show the existence of the |$\alpha+\alpha^*$| cluster structure at the highly excited energy around |$E_x=20$| MeV in |$^{8}$| Be for the first time in the coupled-channel calculations. An extended double-folding model derived using a realistic precise cluster wave function with a well-developed |$N+3N$| cluster structure for the first excited state of |$^4$| He was employed. The calculation reproduces the experimental phase shifts in |$\alpha + \alpha$| scattering up to |$E_{\rm c.m.}=21$| MeV well. The result shows that the well-developed core-excited |$\alpha+\alpha^*$| structure appears as resonances for |$L=0$| and |$2$| near the |$\alpha+\alpha^*$| threshold which correspond to the experimental states at |$E_x=20.20$| MeV and |$E_x=22.24$| MeV in |$^8$| Be. [ABSTRACT FROM AUTHOR]