Anomalous behavior of the first excited 0$^{+}$ state in $N \approx Z$   nuclei
  A study of the energies of the first excited $0^+$ states in all even-even $Z$ $\geq$ 8 nuclei reveals an anomalous behavior in some nuclei with $N$ = $Z$, $Z$ $\pm$ 2. We analyze these irregularities in the framework of the shell model. It is shown that proton-neutron correlations play an important role in this phenomenon. 
K. Kaneko, R. F. Casten, M. Hasegawa, T. Mizusaki, Jing-ye Zhang, E.   A. McCutchan, N. V. Zamfir, R. Kr\"ucken