The Question of Low-Lying Intruder States in $^8Be$ and Neighboring Nuclei

Fayache, M. S.; de Guerra, E. Moya; Sarriguren, P.; Sharon, Y. Y.; Zamick, L.

The Question of Low-Lying Intruder States in $^8Be$ and Neighboring Nuclei

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Description

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