Giant lifetimes of optically excited states and the elusive structure of sodiumnitroprusside

The properties of sodiumnitroprusside (Na2[Fe(CN)5NO]*2H2O) are investigated by density functional theory. The calculated results both for the free anions as well as for the solid show that the ground-state Born–Oppenheimer surface has local minima for sidewards bonded and inverted NO. The calculated properties for the local minima: very long lifetime because of large barrier, diamagnetism, optical excitation energies, vibrational, and Mössbauer properties are in essential agreement with experiment. The present findings elucidate the possibility of population transfers by illumination with light of different wavelengths.