Moessbauer parameters of the two long-lived metastable states in Na2[Fe(CN)5NO].2H2O single crystals

We have measured the quadrupole splitting, isomer shift and line broadening of the ground and two metastable states in Na2[Fe(CN)5NO].2H2O single crystals. Pure state II could be observed by Moessbauer spectroscopy after irradiation of state I with light in the near infrared spectral region. The difference between the two nearly infinitely long-lived electronic states is shown. A possible change of the Fe(3d, 4s, 4p) electron densities is discussed on the basis of the Moessbauer parameters and the ν(FeN) and ν(NO) stretching vibrations. The resulting new orbital population allows to explain the observed properties of state I. A rearrangement of the electron density due to state II would lead to a contradiction with the vibrational behaviour of the molecule. The larger line width of both metastable states could not yet be interpreted. (orig.)