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.

Pulsed illumination of lithium–niobate crystals with green light excites electrons from deep traps into the intrinsic defect NbLi5+ (Nb on Li site in the valence state 5+) and creates NbLi4+ centers (small polarons). The electrons trapped in this more shallow center increase the light absorption in the red and near infrared. The dark decay of the polaron concentration is observed by monitoring the relaxation of these absorption changes. Iron-doped lithium–niobate crystals with different concentrations of NbLi are investigated for various illumination conditions and temperatures. The relaxation shows a stretched-exponential behavior which is in disagreement with the predictions of the standard rate-equation-based model. The observed lifetimes of the polarons range from tens of nanoseconds to some milliseconds. Computer simulations reveal that all results can be explained considering distance-dependent excitation and recombination rates, i.e., the lifetime of an individual polaron depends on the distance to the next available deep electron trap. Based on the new insights, tailoring of lithium–niobate crystals for nonvolatile holographic storage becomes possible.

The dependence of the population dynamics on intensity, time, wavelength and polarisation of the illuminating light and on the temperature of both metastable states in Na 2 [Fe(CN)sNO]. 2H20 single crystals is investigated by differential scanning calorimetry. The population and depopulation behaviour can be described by exponential functions. The wavelength dependence shows the spectral range in which both states can be excited and the existence of a transfer process from state II into state I. Further, light of the near infrared region, transfers state I into state II.