  The parity-allowed two-photon transitions between the ground state 3A2(T2) of
the configuration 3d8 in cubical symmetry and the excited states of the same
configuration are obtained via a simple model. This model is developed in a
symmetry adapted framework by using second-order mechanisms and ionic
wave-functions. It is applied to the recent experimental results obtained by
McClure and co-workers for Ni2+ in MgO.
