Question of low-lying intruder states in [Formula Presented] and neighboring nuclei

The presence of not yet detected intruder states in [Formula Presented] e.g., a [Formula Presented] intruder at 9 MeV excitation would affect the shape of the [Formula Presented]-delayed [Formula Presented] spectra of [Formula Presented] and [Formula Presented] In order to test the plausibility of this assumption, shell-model calculations with up to [Formula Presented] excitations in [Formula Presented] (and up to [Formula Presented] excitations in [Formula Presented]) were performed. With the above restrictions on the model spaces, the calculations did not yield any low-lying intruder state in [Formula Presented] Another approach—the simple deformed oscillator model with self-consistent frequencies and volume conservation—gives an intruder state in [Formula Presented] which is lower in energy than the above shell-model results, but its energy is still considerably higher than 9 MeV.