The Isovector Quadrupole-Quadrupole Interaction Used in Shell Model   Calculations with $\Delta N=2$ Excitations
  The effect of the ``$B$'' term in the interaction $-\chi Q\cdot Q(1+B\vec{\tau}(1)\cdot \vec{\tau}(2))$, which was previously considered in the $0p$ shell, is now studied in a larger space which includes $\Delta N=2$ excitations. We still get a collapse of low-lying states below the conventional $J=0^+$ ground state when $B$ is made sufficiently negative. 
M.S. Fayache, Y.Y. Sharon and L. Zamick