The presence of not yet detected intruder states in 8Be e.g. a J=2+
intruder at 9 MeV excitation would affect the shape of the β∓-delayed alpha spectra of 8Li and 8B. In order to test the
plausibility of this assumption, shell model calculations with up to 4ℏω excitations in 8Be (and up to 2ℏω excitations in
10Be) were performed. With the above restrictions on the model spaces, the
calculations did not yield any low-lying intruder state in 8Be. Another
approach -the simple deformed oscillator model with self-consistent frequencies
and volume conservation gives an intruder state in 8Be which is lower in
energy than the above shell model results, but its energy is still considerably
higher than 9 MeV.Comment: 16 pages (RevTeX), 1 PS figure. To appear in Phys. Rev.