MICROSCOPIC CALCULATIONS OF THE SPECTRA OF LIGHT-NUCLEI

We perform large-space shell-model calculations for the low-lying ener gy spectra of a few light nuclei, He-4, He-5, Li-6, and Li-7, in a no- core model space with a realistic effective two-body interaction (Brue ckner G matrix). Our G matrices are calculated for the Reid-soft-core potential in a harmonic-oscillator basis. Single-particle ''-U'' inser tions are replaced by two-particle ''-U'' insertions and are included in the G-matrix calculations, which sum them to all orders. With the s tarting energy of the G matrix chosen to give approximately the experi mental binding energy, we obtain nuclear energy spectra which are in r easonable agreement with experiment. We also investigate the dependenc e of our results on the size of the model space and on the harmonic-os cillator basis parameter (HBAROMEGA).