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

We show the existence of the α+α * cluster structure at the highly excited energy around Ex =20 MeV in 8Be for the first time in the coupled channels 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 4He was employed. The calculation reproduces the experimental phase shifts in α+α scattering up to Ec.m. =21 MeV well. The result shows that the well-developed core-excited α+α * structure appears as resonances for L=0 and 2 near the α+α * threshold which correspond to the experimental states at Ex =20.20MeV and Ex =22.24MeV in 8Be.