v 1 2 7 O ct 1 99 9 Application of the extended P + QQ force model to N ≈ Z fp shell nuclei

To study collective motion, the extended pairing plus QQ force model proposed recently is applied to A=46, 48 and 50 nuclei in the f p shell region. Exact shell model calculations in the truncated model space (f 7/2 , p 3/2 , p 1/2) prove the usefulness of the interaction. The simple model with the pairing plus quadrupole pairing plus QQ force and J-independent isoscalar proton-neutron force reproduces unexpectedly well observed binding energies, energy levels of collective (yrast) states and reduced E2 The correspondence between theory and experiment is almost comparable to that attained by the full f p shell model calculations with realistic effective interactions. Some predictions are made for energy levels and variations of B(E2) in the yrast bands, in these nuclei. Characteristics of the interaction are investigated by comparing with the realistic effective interactions.