OBSERVED DIFFERENCE BETWEEN THE PROBABILITIES OF RECOILLESS RESONANCE-ABSORPTION F' AND REEMISSION F'' OF GAMMA-QUANTA IN SINGLE-CRYSTALS OF NA2[FE(CN)5NO].2H2O

The recoilless absorption probability factor, f', and recoilless reemission, f", both measured on Na2[Fe(CN)5NO].2 H2O single crystals using the "black" filter technique, were found to be different. Unexpectedly, the results found were f" > f'. In the calculation of f", selfabsorption in the scatterer, non-ideality of the "black" filter and the influence of non-resonant scattering processes have all been taken into account. By varying the scattering geometry for the incoming and outgoing gamma-beam relative to the crystallographic axes only a change in the reemitted values f"a, f"b, f"c could be detected because of the long lifetime of the excited nucleus (approximately 10(-7) s) relative to the lattice vibration frequencies (approximately 10(12) Hz).