Shell model approach to proton-neutron alignment in N~Z Ge-As nuclei

Detailed experiments, including high spin non-yrast states, were, recently, performed for N~Z medium-heavy nuclei, for instance, 66Ge [1], 68Ge [2] and 69As[3]. On the other hand, recently the spherical shell model has become capable of calculating A=60-70 nuclei in the pf5/2g9/2 shell. As residual interaction, isospin invariant extended P+QQ interaction, which has been proposed by Hasegawa and Kaneko, has also become successful in pf shell and pf5/2g9/2 shell. Indeed, our shell model calculations reproduce observed energy levels up to high spins in these nuclei and successfully explain shape changes from 64Ge to 68Se along the even-even N = Z line. In this abstract, we would like to report that various type of particle alignments like two-neutron alignment, one-proton-one-neutron alignment, two-proton-and-two-neutron alignment and so on, become significant, especially for 66Ge, 68Ge and 69As [4]. The figure shows the experimental and theoretical level schemes of 69As, for instance. By evaluating occupation number, partial isospin and partial angular momentum of the g9/2 orbit, the alignment mechanism is clearly shown in our shell model framework. [1] E.A. Stefanova et al., Phys. Rev. C 67, 054319 (2003). [2] D. Ward et al., Phys. Rev. C 63, 014301 (2001). [3] I. Stefanescu, et al. Phys. Rev. C 70, 044304 (2004). [4] M. Hasegawa, K. Kakeko, T. Mizusaki, Phys. Rev. C70 (2004) 031301. Phys. Rev. C72 (2005) 064320, Phys. Rev. C71 (2005) 044301