Two-Photon Spectroscopy of Transition-Metal Ions in Cubical Symmetry
  Symmetry adaptation techniques are applied to the determination of intensities of intra-configurational two-photon transitions for transition-metal ions in cubical symmetry. This leads to a simple model giving the polarization dependence of intensities of two-photon (electric dipolar) transitions between Stark levels of the configuration 3dN (N = even or odd). 
M. Daoud and M. Kibler