SIMPLE APPROXIMATION FOR THE STARTING-ENERGY-INDEPENDENT 2-BODY EFFECTIVE INTERACTION WITH APPLICATIONS TO LI-6

We apply the Lee-Suzuki iteration method to calculate the linked-folde d diagram series for a new Nijmegen local NN potential. We obtain an e xact starting-energy-independent effective two-body interaction for a multishell, no-core, harmonic-oscillator model space. It is found that the resulting effective-interaction matrix elements can be well appro ximated by the Brueckner G-matrix elements evaluated at starting energ ies selected in a simple way. These starting energies are closely rela ted to the energies of the initial two-particle states in the ladder d iagrams. The ''exact'' and approximate effective interactions are used to calculate the energy spectrum of Li-6 in order to test the utility of the approximate form.