Anisotropic holographic scattering in centrosymmetric sodium nitroprusside

Anisotropic holographic light scattering has been discovered in centrosymme tric single crystals of sodiumnitroprusside, Na-2[Fe(CN)(5)NO]. 2H(2)O, in which the photorefractive response is based on the excitation of metastable electronic states. Besides a bright homogeneous scattering corona generate d by isotropic scattering, a sharp scattering ring builds up with light pol arized orthogonal to that of the pump beam and the corona. This anisotropic scattering resulting from interference of scattered waves with the pump be am occurs although there is no linear electro-optic effect in centrosymmetr ic crystals. (C) 1999 American Institute of Physics. [S0003-6951(99)05027-5 ].