Holographic Scattering in CentrosymmetricNa2[Fe(CN)5NO]̇2H2O

Holographic light scattering is discovered in single crystals of sodiumnitroprusside, ${\mathrm{Na}}_2\left[\mathrm{Fe}\right(\mathrm{CN}{)}_5\mathrm{NO}]̇2{\mathrm{H}}_2\mathrm{O}$, although light amplification on the basis of wave mixing is in centrosymmetric crystals forbidden. By excitation of long-living metastable states at temperatures below $T=200\mathrm{}\mathrm{K}$ a radially symmetric intensity distribution appears around the directly transmitted pump beam, which results from diffraction of the incoming light at written parasitic holographic phase gratings. Tilting the crystal the corona turns into two cones of diffracted light as a result of the Bragg conditions.